Produced by Liza Finley and Ryan N. Smith

[This story first aired on March 2. It was updated on Aug. 3.]

In 2015, a team of "48 Hours" producers were filming in Charleston, South Carolina, on another case when they met a mother who told them a story they couldn't stop thinking about — a mystery that has haunted the small town of Moncks Corner since 2008.

Kadie Major, who was married, was found dead alongside a section of railroad tracks. Her little daughter was found drowned in a pond 100 feet away. Back in 2008, Rick Ollic, then with the Berkeley County Sheriff's Office, was in charge of the investigation. Ollic believed it was a murder-suicide and says a note found in Kadie's pocket was a piece of compelling evidence showing that she was delusional at the time.

Kadie's family never believed she was delusional or that she would take her own life.

Her mother, Vicky Hall, vowed to get to the bottom of what happened and pressured investigators to the point where she says they "absolutely avoided me."

Hall embarked on her own investigation — determined to show her daughter did not throw herself in front of a train.

"I remember, I was just walking outside by myself, and I just looked up and I said, 'Kadie and River, I promise you I will do whatever it takes to find the truth,'" Hall tells correspondent Peter Van Sant.

Over the next several years Hall and "48 Hours" stayed in touch and started investigating the mysterious circumstances surrounding the two deaths -- which ultimately led to the reopening of a closed case.

A decade after her daughter's death, Hall finally got her chance to talk with detectives about her case and "48 Hours" was there.

THE MYSTERY BEGINS

Vicky Hall: Before I fell asleep ... I remember ... that train goin' by and ... for some reason, that just burned in my head. And I never knew that my daughter ... and my granddaughter ... would have been laying there, dead.

Every night for the past 11 years, that train has come barreling down the tracks behind Vicky Hall's horse farm in Moncks Corner, South Carolina, near Charleston. And every night the forlorn cry of its whistle brings her grief roaring back.

Vicky Hall: It's just still hard for me to have to believe that that happened to them. ... and the hardest thing, I guess, is to know how much they suffered.

"Kadie just loved River Lynn with all of her heart. She was so proud of her, she loved being a mother," Vicky Hall says of her daughter, seen in home video with River Lynn. "She was just a person that was so full of life." Vicky Hall

From day one, Hall did not believe her daughter Kadie, 5 months pregnant, drowned her baby daughter, River Lynn, then jumped in front of a train.

Vicky Hall: A pregnant woman doesn't walk three-fourths a mile down a railroad track in pitch dark night. ... There's no way Kadie would have ever, ever killed River or herself. ... I believe this is a cold-blooded murder.

Rick Ollic, who led the investigation back in 2008, didn't see it that way.

Peter Van Sant: You believed that she was walking along these railroad tracks carrying her daughter River with suicide on her mind?

Rick Ollic: That's what we believe.

Rick Ollic says the note found in Kadie Major's pocket was a piece of compelling evidence showing that she was delusional at the time. Berkeley County Sheriff's Office

Ollic says they found a note in Kadie's pocket which he believes is compelling evidence that she was delusional — obsessed with reading about end of the world conspiracies on the internet. Among the scribblings was this: the Antichrist could be a woman.

Rick Ollic: There were some things that were in that note that made me believe that she was buying into this spiritual warfare that she had going on in her life.

Vicky Hall: I just remember them looking at me in the eye and saying, "Your daughter had a mental illness, and she did this."

Officially, the manner of 10-month-old River Lynn's death was undetermined. But unofficially, investigators believed Kadie murdered her — a branding that almost destroyed Hall, says her brother Chad Dillinger.

Chad Dillinger: She'd call me in the middle of the night. ... She'd just scream for hours ... like the worst death scream that you can — you can't even imagine.

Vicky Hall: I couldn't hardly function, couldn't keep running the farm well. I didn't want to go to the grocery store because everywhere I would go to I would see them. . it just made no sense that they weren't here. Nothing made sense.

Desperate for answers, Hall started her own investigation: gathering documents, keeping meticulous notes -- anything to find the truth.

Chad Dillinger: She kept fighting and fighting and fighting and fighting ... She wouldn't let anybody tell her different. It's really took its toll on her.

Vicky Hall: I turned to alcohol. ... trying to numb my pain ... but actually all it did is make everything worse

With the help of some good friends and a strong dose of faith, Hall stopped drinking.

Vicky Hall: I remember saying, "OK, Vicky, you can either let this kill you and destroy you ... or you can try to ... make Kadie and River proud of you and pull it together."

Hall got her horse business back on track, then did something she never thought she'd do with the paperwork from her private investigation.

Vicky Hall: I couldn't fight no more for a while. I had to grieve and take time for me for a while. Some friends just said, "Vicky, just put everything in the box. Put all your papers in a box and stop looking at it and put it in God's hands."

Vicky Hall: So, I put everything back in the box and I closed it and I locked it. … and I put it in my closet.

But Hall never forgot that promise to clear Kadie's name and show the world who her daughter truly was: a kind-hearted 26-year-old who loved horses and her family.

Ken Dillinger | Kadie's uncle: It was a smile, I mean there was a perma-grin on her face, and … It was always lit up, always lit up.

Sarah Watford: She was better than most people -- just had a giving heart, just a true genuine person.

Sarah Watford is Kadie's little sister. Kadie, 12 years older, was like a second mother.

Sarah Watford: I just think of what a good mom she was and how I want to be a good mom like her. …And she's the person that I want to be.

Kadie, holding River Lynn, and Aaron Major. The couple, who were high school sweethearts, married in 2003. Vicky Hall

Peter Van Sant: What were Kadie's dreams in this life?

Vicky Hall: She was living the perfect life for her. That's what Kadie wanted to be, was a mother, have children, be a wife, take care of her house, cook, garden … She was livin' her dream. She really was.

Kadie had married the love of her life in 2003, her high school sweetheart Aaron Major.

Vicky Hall: they really were just like best friends.

Aaron went to work for Kadie's dad, who was a housepainter. She settled in as a homemaker. In 2007, they welcomed River Lynn.

Vicky Hall: And she had this beautiful little smile that made her just look like an angel.

Hall says Kadie had never been happier.

Vicky Hall: She was so excited about having children and she wanted a big family.

Not long after River was born, Kadie got pregnant again; this time, she learned, with a son. She was so excited, she gave the unborn child a name: Aadon.

Peter Van Sant: What was her reaction to that?

Sarah Watford: She just couldn't stop smiling.

But, just one day later, that perfect world came crashing down.

Hall and her husband Jeff were awakened at 1:44 a.m., when Aaron suddenly showed up at their home.

Vicky Hall: I remember telling myself, "Oh My God … what is wrong? Why is Aaron here sitting on the porch? He's never come in the middle of the night."

Hall says he told her when they arrived home after Aaron finished working, Kadie started acting paranoid and stood in the doorway with River, refusing to enter.

Vicky Hall: He said when Kadie got home she said she had a premonition that someone was gonna kill her … He said, "She's standing there shaking and trembling … And she wanted to go get a hotel."

Vicky Hall: And he said, "I told her let me go take a shower. … and then I'll bring you wherever you want." … he said he went and took a shower." He heard her truck start … and she's gone.

Then, Hall says, out of the blue, Aaron suddenly started going off on a string of bizarre conspiracy theories.

Vicky Hall: Like the world's coming to an end and, you know, the government blew up the Twin Towers. … I … asked him … why are you talking about this?

Vicky Hall: … that's the moment everything changed -- that moment.

STRANGE BEHAVIOR

Kadie and River Lynn had now been missing for more than 12 hours in stormy, icy conditions. Vicky Hall and Kadie's husband, Aaron Major, set out searching for her truck at local motels and on the back roads of Moncks Corner but Hall says, something seemed off with Aaron.

Vicky Hall: I'm looking at every car coming … trying to see her truck. … and he's just not looking … and I'm like to myself, "Why is he not looking? Why is he not looking?"

Then, the usually quiet Aaron started talking -- not about Kadie, but about those same strange theories.

Vicky Hall: Still that same stuff about the Twin Towers just being a conspiracy.

Back at Kadie's house, Sarah Watford was waiting alone in case her sister came home. She noticed a highlighted Bible passage on the kitchen table.

Peter Van Sant: What did you read in those papers?

Sarah Watford: The thing that that stands out that I read that I will never forget is that the first born son is to be sacrificed. … I knew something wasn't right.

Frightened, Watford immediately called her mom to come get her. When Hall and Aaron picked her up, both mother and daughter noticed something that would become etched in their memories: Aaron's hand.

Vicky Hall: He had lifted his hand up … And I'm like, "Oh my God, why is his hand so big?" … What I didn't know at that moment is Sarah saw it, too

Sarah Watford: It just almost looked like a monster's hand, you know? It just looked fat. His whole fingers was swollen.

Was it connected to Kadie's disappearance? Hall filed that detail and the other red flags in the back of her mind and went out searching on her own. Then, at 11:31 a.m., came a call from Aaron that would alter the course of her life.

Vicky Hall: He said … "I heard on the radio that there's, uh, an accident. A train hit a vehicle on Oakley Road and two people are dead."

Hall headed straight to Oakley Road, but there was no train, no vehicle, no sign of a collision. Then, as she was leaving, she spotted Kadie's truck – undamaged -- about 500 feet from the tracks.

Vicky Hall [at railroad tracks]: And I just fell on my knees and collapsed,' cuz I knew it wouldn't make any sense. Her truck should never be here, right here.

Aaron was her first call.

Peter Van Sant: You tell him that you have found the pickup truck. Does he cry out?

Vicky Hall: No. Not at all.

Investigators at the scene where Kadie's body was found beside the train tracks; her little daughter was found drowned in a pond 100 feet away. Kadie's truck – undamaged -- was found about 500 feet from the tracks. Berkeley County Sheriff's Office

By then, a forensic team was at the death scene over half a mile down the tracks. A railroad worker had discovered the bodies around 8:20 that morning. Kadie, they believed, had been struck on her side by some object hanging off the train. She had deep lacerations across her lower abdomen and right thigh.

Rick Ollic of the Berkeley County Sheriff's Office delivered the shattering news.

Vicky Hall: Captain Ollic is right there and I'm just looking him in the eye, and I just remember his face. And he told me they were dead. … I'm numb … just totally broken, just totally dead, totally devastated. Totally devastated.

That night, Aaron was asked to give a written statement to authorities. Claiming he was too emotional to write, a detective wrote it for him. There was no mention of a swollen hand.

In his statement, Aaron said she was acting so paranoid "that I couldn't reason with her… just wanted to leave the home feeling that someone was out to kill her."

Aaron told a version of that story to Kadie's uncles, adding that she was suffering from postpartum psychosis.

But with every telling, crucial details changed. In one story, Aaron said Kadie refused to enter the house because she was panicked, in a state of paranoia. In another version, he says she did go in to feed the baby.

Peter Van Sant: What does that suggest to you, the fact that he's told different stories?

Ken Dillinger: Pretty much cut and dry that he doesn't have his stories together of what really happened, and every time he thinks about it, he doesn't remember what he said.

Kadie and Aaron Major, parents of daughter River Lynn, were expecting a son. Vicky Hall

The family was suspicious. And Sarah Watford, remembering that swollen hand, was convinced that Aaron broke it while killing her sister.

Sarah Watford: It just made me think, like, did he hit his hand on the train … pushing her into the train, or fighting with her? … that's what made me know in my heart, in my head, that he was involved.

Both Watford and Hall say they had seen Aaron's injured hand the morning the bodies were discovered. But Ollic's investigation turned up another explanation: that Aaron injured it two days later at the funeral home when he punched a wall while choosing a coffin.

Rick Ollic: We inquired with the funeral director and she said, "Yes, I witnessed him punch a cinder block wall."

At first, Aaron tried to make the funeral private, telling Vicky and her family they were not invited.

Vicky Hall: Everything was a fight from the very moment they died to have things done normally.

Mother and daughter were in the same coffin. Miraculously, Kadie's face was largely undamaged and the family wanted an open casket for Kadie and River. But Hall says Aaron took it a step too far.

Vicky Hall: He wanted Aadon, the unborn son, displayed publicly for viewing on top of Kadie. … I'm like "Aaron, no."

That wasn't the end of his bizarre behavior at the viewing, says Chad Dillinger.

Chad Dillinger: He was just sitting there nonchalantly on the front pew eating McDonald's. … drinking out of his big McDonald's cup.

Peter Van Sant: The dead bodies of his family are right in front of him.

Chad Dillinger: He could reach out and touch 'em. … He never shed a tear, he never came and hugged anybody. It was the sickest thing I ever witnessed in my whole life.

Two days after the funeral, Aaron went in for surgery to mend his broken hand.

The next day, eight days after his wife and baby died under mysterious circumstances, Aaron, with a freshly bandaged hand, was finally brought in to the Sheriff's Office for questioning:

DET. JERRY MERRITHEW: You have anything to do with your wife's death?

AARON MAJOR: No. DET. JERRY MERRITHEW: You have anything to do with your child's death?

AARON MAJOR: No. DET. JERRY MERRITHEW: If you knew what happened, would you tell us? AARON MAJOR: Mhm.

But by then it was too late, says private investigator Jessica Sanders. The coroner had already issued a preliminary ruling of suicide, later made permanent.

Peter Van Sant: How would you describe the quality of the original investigation done?

Jessica Sanders: Horrible … they dropped the ball in every way here.

OPENING PANDORA'S BOX

By day, Jessica Sanders, the mom, is busy taking care of her children – all five of them. But by night, Jessica Sanders, the private eye, is at the gun range or on the road with cameras and disguises in hot pursuit.

Jessica Sanders: I catch cheaters and anyone who's lying pretty much.

Peter Van Sant: Is that your specialty -- cheating husbands and wives?

Jessica Sanders: Mostly, yes.

Peter Van Sant: How's business?

Jessica Sanders: Good [laughs]. Business is good.

SANDERS WEB EXTRA

Vicky Hall met Sanders four years after Kadie's death. She suspected her now ex-husband was having an affair and hired Jessica to investigate.

Jessica Sanders: We became very close. You know, she had lost Kadie and I had actually lost my mom. And we just -- we bonded.

Sanders says she saw Hall through some of her darkest years as she battled to get the Berkeley County Sheriff's Office to take another look at the case -- and another look at Aaron Major.

Jessica Sanders: Vicky was really up against the department that had their mind made up. … she always had questions and none of them were answered.

That changed in 2015, seven long years after her daughter's death. "48 Hours" producers got a tip about Vicky's case and that box of evidence she had locked up so many years ago. They wanted to know more.

Vicky Hall: I realized it was time to get started back on the case.

Hall asked her private investigator pal to help.

Peter Van Sant: Did you open the box?

Jessica Sanders: I did … it was like Pandora's box … it's unbelievable at all the information that she had and how badly this case was handled. It didn't take 30 minutes of looking at it to be in, like, shock.

Jessica Sander and Vicky Hall in the "war room." CBS News

Together Sanders and Hall built the "war room." They covered the walls with timelines and facts about the case, determined to find the truth -- whatever that might be.

Vicky Hall: If you can tell me I am wrong, and my daughter really committed suicide … tell me I'm wrong, please … the last thing I wanted was her to die at the hands of her husband.

Vicky Hall: … we could not exclude it, we tried.

Rick Ollic explains his theory to "48 Hours" correspondent Peter Van Sant. CBS News

Peter Van Sant [at the train tracks]: So, is your opinion of what happened out here that this essentially was a murder/suicide?

Rick Ollic: That's my theory…

Rick Ollic: We worked this case for months. We believed we unturned everything there was to unturn at the time.

Rick Ollic, now the chief of police at the Moncks Corner Police Department, maintains he considered Aaron Major a suspect.

Peter Van Sant: Did you suspect foul play?

Rick Ollic: I always suspect foul play until proven otherwise.

But he never found proof that Aaron killed his wife.

Rick Ollic: We were never able to connect the dots.

He says the evidence -- Aaron's statements and that note in Kadie's pocket with scribblings about the Antichrist -- all pointed to a woman in deep psychological turmoil.

Rick Ollic: There was information that she was going through some type of spiritual warfare in her life.

He believed Aaron's story that Kadie's actions were driven by postpartum psychosis.

Rick Ollic: She was alive when the train struck her … to me it was self-inflicted.

Two months after the suicide ruling, Hall hired a forensic psychologist in the hopes of proving Ollic wrong. But the psychologist's report said there was not enough evidence to "overcome the presumption of suicide."

Vicky Hall: I knew she wouldn't do that, wouldn't be capable of doing that. But Aaron's behavior … he's not acting normal, he's not acting right. …He's got a broken hand, talking crazy things that never once came out of Kadie's mouth.

"She was very happy, she was very excited to have a boy," says Vicky Hall of her daughter, who was 5 months pregnant when she died. Vicky Hall

As for that note in Kadie's pocket, Hall believes Kadie was documenting her husband's internet searches on their family computer.

Vicky Hall: I believe she wrote these notes down on this paper because she was seeing what Aaron was reading … and seeing what he was believing in and it was scaring her and she was just making notes of all the titles on the computer.

Hall and Sanders went to work determined to show that Kadie was not psychotic. They spoke to a dozen witnesses, including Kadie's Obstetrician Dr. Christine Case who examined her the day before her death.

Dr. Christine Case: I do not think is -- in my professional opinion, that she had any depression or postpartum depression.

Back then, Ollic and his team did not speak to Dr. Case, and Hall says would not listen to what she had to say.

Peter Van Sant: She says she was never questioned about her daughter's state of mind and what had happened in the hours on that day that she disappeared. How could someone not have interviewed the family about those things?

Rick Ollic: I don't recall when she was interviewed, and they should have been interviewed for those things.

Peter Van Sant: What I'm holding here, Vicky gave us. It's dozens and dozens of pages of emails that she said that she sent to you during that time, and you didn't answer one of these.

Rick Ollic: I don't recall.

And Hall says, they should have been more suspicious of Aaron's story about Kadie's alleged paranoia the night she disappeared.

AARON MAJOR [interrogation] She got more and more, like, paranoid about me, and started -- completely not trustin' me at all.

Jessica Sanders: in his story she's shaking, trembling, scared.

But Sanders says phone records show during that time Kadie called her mom and Hall says she sounded perfectly normal.

Jessica Sanders: When she called Vicky, she was wanting to go eat dinner with her. This is not a person who's frantic.

Sanders says, the more she dug, the guiltier Aaron looked. Most ominously, a computer search he made early in the morning before the family was notified Kadie and River were dead.

Jessica Sanders: That morning, he had searched "two dead in Berkeley County."

Peter Van Sant: So why do you think he was Googling that?

Jessica Sanders: Well, I think he was Googling that because he was trying to find out if the bodies had been found yet. He's trying to determine his next move.

They believe that next move was his call to Hall saying he heard on the radio that two people were killed in a train accident on Oakley Road.

Vicky Hall: I called every radio station, I went to the TV stations after they died … I searched and searched for years, not one person could tell me Oakley Road was ever on the TV or the radio.

Peter Van Sant: If there was in fact not a news broadcast … How would he have known that location, that there'd been an accident there?

Rick Ollic: I have no -- I have no re -- ... I have no idea how he would know.

Peter Van Sant: Is this suspicious to you?

Rick Ollic: Absolutely.

Sanders says there's only one reason he would have known.

Jessica Sanders: He knew, because he's the one that put 'em out there.

Hall and Sanders say there were more damning clues back at the house.

Vicky Hall: Some stuff was knocked off of River's dresser. There was clothes on the floor. All of these drawers were all open in the whole bathroom.

Peter Van Sant: What does that suggest to you?

Jessica Sanders: There was a fight. I believe 100 percent there was a fight and she was trying to leave him.

Peter Van Sant: Do you believe that Kadie Major may have died inside her own house?

Jessica Sanders: I do. I think it's very possible that she died at the house.

Their house – a potential crime scene – was never properly processed.

Jessica Sanders: There's no photos.

Peter Van Sant: No forensic search of the house.

Jessica Sanders: No forensics at all. … If there was a fight that started there, Luminol test. Easy. They did nothing.

And Aaron Major, who Ollic admits was a suspect, was allowed home unaccompanied the night his wife and daughter were found dead.

Peter Van Sant: He could have altered a potential crime scene and no one went there to check that. Correct?

Rick Ollic: Possibly.

Peter Van Sant: Family members who had been inside that house claim it was in disarray, that things had been thrown about. 24 hours later it had all been cleaned up. Is that true?

Rick Ollic: I don't have an answer to that cuz I don't recall when we went. I mean, I'd have to review back to the case, it was 10 years ago.

But a lot can happen in 10 years.

Det. Darrell Lewis There's a new sheriff in town.

And a new cold case team.

Peter Van Sant: Do you believe today that Kadie Major committed suicide?

Lt. Dean Kokinda: No.

Det. Darrell Lewis: No.

A NEW LOOK AT THE CASE

Things were changing fast in Moncks Corner. In 2015, new Sheriff Duane Lewis swept into town with a brand new attitude.

When two "48 Hours" producers called him asking about the Kadie Major case, he listened.

Sheriff Duane Lewis: I was not familiar with the case. … but I asked my cold case detectives to locate the file … so that when I did meet with Vicky we could … have some knowledge about the case.

After 10 years of heartache, Vicky Hall is finally getting the chance to talk to Berkeley County detectives about her case. And "48 Hours" was there to document it.

Vicky Hall: For justice to happen would be the best news of what really happened that night.

Sheriff Lewis had assigned Lt. Dean Kokinda to take a second look. Hall, long the target of country gossip, first had to clear a big hurdle.

Lt. Dean Kokinda: Vicky … had a reputation … that she was crazy. … So I wasn't looking forward to meeting with her. But … when she came in … I talked to her for a couple hours, I was like, "Well, she's not crazy."

Vicky Hall [to detectives]: And when she's shaking and trembling how is she holding River?

Lt. Dean Kokinda: She had valid questions and they weren't answered.

Vicky Hall meets with Lt. Dean Kokinda and Det. Darrell Lewis, the new investigators on the case. CBS News

She also had a lot of information to share with Lt. Kokinda and a detective brought out of retirement to help him: the sheriff's little brother, Darrell Lewis.

Det. Darrell Lewis: When I walked in the door, he goes, "I need you to look at this … something's wrong with this case."

To begin with, Lewis says blood and tissue spatter evidence show that the original investigators got the wrong train.

Det. Darrell Lewis: Originally, they said a southbound train hit her. The evidence shows it was a northbound train. What else did they get wrong? … What else did they miss?

Lewis quickly answered his own question. They missed their one and only opportunity to ask Aaron the tough questions during their interrogation:

DET. JERRY MERRITHEW: What do you think happened? AARON MAJOR: I don't know what happened.

Det. Darrell Lewis: You call it an interrogation, we call it an interview.

During questioning in 2008, the investigator never asked Aaron Major about his bandaged hand. Berkeley County Sheriff's Office

The investigator never even asked Aaron about that hard to ignore bandaged hand and he never challenged Aaron's version of events, including Kadie's supposed breakdown:

AARON MAJOR [interrogation]: She just got real paranoid, and, quit trustin' people and stuff.

Peter Van Sant: Are you buying Aaron's story that she was out of her mind?

Lt. Dean Kokinda: No.

Det. Darrell Lewis: No. He's the only person who's said this.

Lewis and Kokinda did what Ollic and his team didn't do -- talk to Kadie's closest friends and family.\

They discounted that psychological report because they say it was based largely on Ollic's investigation. They quickly ruled out postpartum psychosis.

Lt. Dean Kokinda: You can hide depression from your friends and family, but you don't hide paranoia.

And they didn't believe that Kadie could or would have made that 6/10th of a mile walk in pitch black on gravel in the rain and sleet carrying a 30-pound baby.

Lt. Dean Kokinda [walking where the bodies were found]: If she wanted to kill herself, she parked right here. She could walk right here. She does have to walk sixth-tenths of a mile down there to get hit by the train. She can get hit 10 feet from her car.

Lt. Kokinda thinks, like Sanders and Hall, the trouble started back at the house.

Lt. Dean Kokinda: We believe that night there was a fight … Some argument whether it be … verbal or physical.

The note and wedding rings found in Kadie's pocket. Berkeley County Sheriff's Office

Which may explain how Aaron injured his hand, says Kokinda. And why they found $1,000 in cash in Kadie's truck and her wedding rings were not on her finger, but in her pocket.

Lt. Dean Kokinda: To me that is very symbolic of her ending the relationship.

Just weeks into their investigation, the cold case team became convinced it was not a suicide. But they still had a lot of questions.

Lt. Dean Kokinda: Why is she on the tracks in the first place? That's the million-dollar question right now.

Among their many theories, maybe an answer to that question: that Kadie fled the house after a fight, drove her pickup truck to the tracks, got out and ran with Aaron giving chase. He caught her and threw her against the train.

Lt. Dean Kokinda: That's a possibility.

Peter Van Sant: She could have been thrown and struck by the side of the train?

Lt. Dean Kokinda: Absolutely.

Another possibility, as Sanders believes, Kadie was killed elsewhere and dumped at the tracks.

Det. Darrell Lewis: I've never ruled out that it could be a staged crime scene.

Peter Van Sant: There's a possibility she was in fact dead at the time this train struck her?

Lt. Dean Kokinda: I think that's one of the possibilities, yes.

Another mystery: just how did River Lynn get in the water 100 feet from the spot where her mother's body was found?

Lt. Dean Kokinda: We don't know how River came into contact with the water.

Kokinda says the cold case unit has confirmed that Aaron told the original detective a huge lie -- a potential game changer:

AARON MAJOR [interrogation]: That's when I heard on talk radio 94.3 that there had been a person and a young child hit by the train in Berkeley County …

Lt. Dean Kokinda: There was no radio report.

Peter Van Sant: There was no radio report?

Lt. Dean Kokinda: Uh-huh.

Peter Van Sant: Why would he have told a story about hearing this report, do you think?

Lt. Dean Kokinda: I think he wanted Kadie and River found.

The team would like to ask Aaron about those lies, but there's a problem.

Peter Van Sant: Aaron Major, is he cooperating with you guys?

Det. Darrell Lewis: No.

Peter Van Sant: Is that a red flag for you?

Det. Darrell Lewis: It is for me 'cause I'd wanna know what happened to my child, my unborn child, and my wife.

"48 Hours" would like to speak with Aaron Major as well.

FIGHTING FOR THE TRUTH

There have been many dark days, but one memory above all else has kept Vicky Hall fighting for Kadie and River.

Vicky Hall: The night they died … and Sarah was there, my daughter … I looked out the window, we have a pond right there … and there is a cross on my pond.

Vicky Hall: And every night me and Sarah would go stand in that door. And we'd look out, and that cross never came back.

Hall believes Kadie and River will never be at peace until Aaron Major is brought to justice.

Kadie and River Lynn Major Vicky Hall

She rarely sees the man she believes put her daughter and granddaughter in their graves, but she says he has harassed the family for years -- even at the cemetery.

Vicky Hall: If we put something there … it would be thrown in the woods and destroyed, broken.

Hall called the authorities and they confronted Aaron, who then returned some of the items he had taken -- including a toy version of Kadie's favorite horse.

Vicky Hall [holding the toy]: When he returned it, the tail was cut off, it was just very upsetting.

Hall suspects he also put a doll with a hole in its stomach at the makeshift memorial where Kadie and River's bodies were found.

Vicky Hall: On the cross is this old, nasty-looking doll. And I just know Aaron put that there to freak me out.

Jessica Sanders: It's disturbing. It's almost like psychological warfare.

Out of all his alleged scare tactics, the most heartless, says Sanders, is video shot by Aaron 10 months after Kadie and River's deaths and laid it on their grave.

Video shot by Aaron Major 10 months after the deaths of his wife and daughter shows River Lynn's high chair pulled up to the table with a jar food on it. Berkeley County Sheriff's Office

Jessica Sanders: He allowed it to look like they were still living there. Like he had River's high chair pulled up to the table with jar food on it, a pillow stuffed in the bed where Kadie would sleep as if she's laying in the bed. … Psychopathic behavior to me.

After his wife and child died, Aaron moved in with his parents in Charleston, about a 40-minute drive from Moncks Corner. He started his own house painting business. "48 Hours" found him at home washing out his fishing gear and in the church parking lot with his mother.

Sanders, who has been studying his movements, says he spends a lot of time alone outside.

Jessica Sanders: This guy, he goes hunting, goes fishing, he's living the life.

But life was about to get a lot harder.

Sheriff Lewis decided to let Aaron know he hasn't been forgotten and announced the re-opening of the case in a very big, public way.

Vicky Hall, center, is surrounded by investigators and family as the case into the deaths of Kadie and River Lynn is reopened. CBS News

SHERIFF LEWIS [to reporters]: Initially it was believed that Kadie was suicidal and had some psychological issues. I can tell you that that is not the case.

Vicky Hall then stepped up to the microphone.

VICKY HALL [to reporters]: Thank you to this sheriff's department. I wanna thank Charleston county. "48 Hours," because we would not be standin' here today if it wasn't for them.

And she didn't mince words when it came to Aaron Major.

VICKY HALL [to reporters]: I believe that Kadie and River and Aadon were murdered by Kadie's husband, Aaron Robert Major. And that's what I believe.

Investigators continue digging, but say, for now, they don't have enough evidence to make an arrest. They are, however, for the first time publically naming Aaron Major the prime suspect.

Lt. Dean Kokinda: Right now, he's the only one we're looking at

Peter Van Sant: Is there anything you'd like to say to Aaron major right now if he's watching?

Lt. Dean Kokinda: Yeah, come talk to us. Tell us what happened cuz what you told us before is not the truth.

"48 Hours"' Peter Van Sant questions Aaron Major about the deaths of Major's wife and daughter. CBS News

"48 Hours" asked Aaron Major to speak with us on camera, but he declined through his attorney. So "48 Hours" went looking for him and found him in the parking garage of an apartment complex.

Peter Van Sant: Hey, how you doing. Peter Van Sant CBS News. You are the only suspect in the deaths of your family. What do you have to say about that?

Aaron Major: I'm not going to comment on this.

Peter Van Sant: Why not? You can tell me whether or not you murdered your family

Aaron Major: Because I don't have any comments at this time.

Peter Van Sant: Nothing whatsoever?

Aaron Major: No.

Other worker: You need to leave please. Leave.

Aaron Major continues to live the life of a free man -- something Hall blames on the original investigator, Rick Ollic.

Peter Van Sant: This beloved young mother was made out to be some depressed child killer. Would you be willing to apologize if it turns out you were wrong?

Rick Ollic: Always do the right thing, it's always important at any time to do the right thing.

It's been 11 years since that cold, wet January morning. No matter how long it takes, Vicky Hall will battle on until the truth is found.

Vicky Hall: You know, we can't bring them back and that's what I would love more than anything … but justice needs to be served. … I will fight for this till the day I die. … I know she's up in Heaven sayin', "You go, Mom. You go."

The Berkeley County Sheriff's Office was so impressed with the investigation by Jessica Sanders, she was offered a job. Sanders decided to continue working as a private investigator.