Story highlights FBI is looking into the death of Lennon Lacy, 17, and the investigations that followed

Lacy was found hanging from a tree after he went for a walk on a summer night

His mother says he did not commit suicide

Claudia Lacy says she can accept anything: even that her youngest son committed suicide -- if it's proven and explained to her.

However, she says, local and state investigators have done neither to support their theory that Lennon Lacy hanged himself one summer night.

"That's all I've ever asked for: what is due, owed rightfully to me and my family -- justice. Prove to me what happened to my child," Lacy says.

She says she's long lost confidence in the Bladenboro Police Department and the North Carolina State Bureau of Investigation.

Now, the FBI is looking into Lacy's death and the local and state investigations that followed.

Without clear answers, the past few months without him have not been easy.

"I look for him and I don't see him. I listen for him and I don't hear him," Lacy says.

The last time Lacy saw and heard her son was August 28. Lennon, 17, played the lineman position for the West Bladen High School Knights, and was focused on football.

His family says that night, he packed a gym bag, washed his ankle brace and hung it on the clothesline to dry before heading out for an evening walk.

The teen had asthma, his mother says, and a doctor had recommended he exercise outdoors at night when the temperature and humidity dropped. Around 10:30, Lennon left his family's small apartment and headed down a dirt road.

His family never saw him alive again.

Just before 7:30 the next morning, he was found hanging from the frame of a swing set in the center of a mobile home community. According to medical documents, his body was covered in fire ants.

Lennon's mother was called to the scene several hours later, after he'd been placed into a body bag.

"It was unreal. It was like a dream. It was like I was not seeing what I was seeing," Lacy says.

Immediately, Lacy believed her son's death was the result of some foul play.

"He didn't do this to himself," Lacy says.

She believes Lennon was lynched.

"He may have either been strangled somewhere else or been placed there or he was hung there while people were around watching him die," Lennon's older brother, Pierre Lacey says.

However, North Carolina's Chief Medical Examiner Dr. Deborah Radisch declared his death a suicide.

When a state investigator asked Lacy if her son had been depressed recently, she told them he had -- because a relative had died recently. The state medical examiner cited that exchange in the autopsy report. Lacy says she did not mean that her son had been suffering from depression.

"When you just lose someone close to you, you're going to be depressed, upset, in mourning," Lacy says.

The family says Lennon had not changed his routine and was focused on college and football -- and distracted by his girlfriend.

The teen had been dating a 31-year-old white neighbor. The age of consent in North Carolina is 16. Some people in their small, southern town did not like that the two were together. Lacy did not like their drastic age difference.

"I was shocked, disappointed. I also, initially told him how I felt - that I did not approve of it," Lacy says.

In the wake of his death, some wondered whether Lennon had been killed because he was in an interracial relationship.

A week after Lennon was buried, a local teenager was arrested for defacing his grave.

"There are too many questions and it very well could be a lynching or a staged lynching. We don't know -- but what we do know is there has to be a serious and full investigation of these matters," says Rev. William Barber, a national board member for the NAACP.

The NAACP hired Florida-based forensic pathologist Christena Roberts to analyze the case and Dr. Radisch's autopsy, completed for the state.

Roberts' first concern: basic physics. Lennon was 5-foot-9. The crossbar of the swing set frame he was found hanging from was 7-foot-6, according to the NAACP review. With no swings or anything at the scene on which he could have climbed, according to the review, it's unclear how Lennon reached the top.

"His size, his stature does not add up to him being capable of constructing all of this alone - in the dark," Lennon's brother says.

According to the 911 recording and the initial police report, a 52-year-old woman got the 207-pound teen down, while she was on the phone with an emergency dispatcher.

"Dr. Radisch also noted that she was not provided with photographs or dimensions of the swing set. Without this information, she would be unable to evaluate the ability to create this scenario," according to the NAACP review.

Lacy says she told investigators that the belts used to fashion the noose did not belong to Lennon.

"I know every piece and every stitch of clothes this child has -- I buy them, I know. Those were not his belts," Lacy says.

The Bladen County Coroner and Medical Examiner Hubert Kinlaw believed the belts might have been dog leashes.

Radisch thought that "some portion must be missing because there was no secondary cut in either belt. The cut would have been necessary to bring down Lennon's body," according to the review.

Also, the shoes Lennon was wearing when his body was found were not his, according to his family.

Lennon's brother says he left home that night wearing size 12 Air Jordan's. However, he was found wearing size 10.5 Nike Air Force shoes. Those shoes were not with Lennon's body when he arrived at the state medical examiner's office, according to the NAACP review.

"He's going to walk a quarter mile from his house in a pair of shoes that's two sizes too small after he takes off his new pair of shoes - and this is a 17-year-old black kid with a brand new pair of Jordan's on. He's going to take those Jordan's off and just get rid of them and put on some shoes that's not his -- we don't know where he got them from, no laces in them -- and continue to walk down this dirt road late at night to a swing set in the middle of the trailer park and hang himself," Lacey says.

"How can I believe that?" Lacey added.

There are also questions about who first declared Lennon's death a suicide.

"Dr. Radisch noted that her determination of (manner of death) in this case as suicide was based on the information she was provided by law enforcement and the local medical examiner. She would have likely called the (manner of death) 'pending' while awaiting toxicology and investigation but the (local medical examiner) had already signed the (manner of death) as suicide," according to the NAACP review.

However, in the summary of the case, written the day Lennon was found, the local medical examiner asked "did he hang self? Will autopsy tell us?" Kinlaw also left the conclusion on the manner of death "pending."

Local police and state investigators declined to speak with CNN. CNN asked to interview Radisch about the statements attributed to her in the NAACP review. Instead, a department spokesperson confirmed the exchanges through a written statement:

"The comments that were released by the NAACP were a synopsis of a professional exchange between the NAACP's independently-retained forensic pathologist and Dr. Radisch," according to a spokesperson for the North Carolina Department of Health and Human Services.

Lennon's family believes there was a rush to judgment. And until someone clearly explains and proves how her son died, Lacy says she'll keep fighting until she gets answers.

"I take it one day at a time. That's all I can say," Lacy says.