Logan Schiendelman was last seen on May 19, 2016 in Tumwater, Washington. Was he the victim of foul play, or is he lost, not wanting to be found?

Logan Schiendelman's high school days in Tumwater were filled with friends, fun and football. His athletic ability, all-American good looks and easygoing attitude brought lots of friends.

But according to his grandmother, who didn't initially return our phone calls, but did answer the door when we showed up,

The good times Logan had in high school didn't follow him after graduation.

"He changed a lot," said Ginnie Gebo, Logan's grandmother. "He had a couple things happen right after high school that made him really aware of racism that he hadn't really thought about as much, and he really had decided that his friends weren't really his friends any more."

Ready for a fresh start, Logan Schiendelman enrolled at Washington State University, more than 300 miles from home.

"His first year at college I think turned out to be very unpleasant for him, and I don't think he had a lot of friends there," said Mike Ware, Logan's uncle.

And his close friends from high school, he'd all but forgotten.

"I had contacted him a bunch of times after we graduated. I'd message him on Facebook. He would read them but never reply," said Dakota Tresner, one of Logan's high school classmates.

After his freshman year at college, and still unsure what he wanted to do with his life, Logan returned to Tumwater to live with his grandmother and half-sister. But friends say he wasn't the same happy-go-lucky Logan.

"He came into my work and brought an application in and I was just like, 'Hey, good to see you, how are you doing?'" said Alyssa Parrish. "And he didn't say much, he kind of got nervous when I saw him. It was very weird."

For the next year Logan kept busy working odd jobs around town.

Then one Thursday morning in May his grandmother was getting ready for work when Logan said something she thought was a bit bizarre.

"He was really nervous and he said he'd had an epiphany and he was driving around, and I said 'Well, talk to me tonight when I get back from home,'" said Ginnie Gebo.

But that talk didn't transpire.

"Of course I wish I would've said 'Sit down, let's talk about it,'" said Gebo.

That was the last time she spoke to Logan Schiendelman.

"The next day I 'pinged' his phone and it pinged near his mom's house, so I thought 'Well, he went over there, was visiting with her,' so that was OK," said Gebo.

It wasn't OK. Logan wasn't with his mother in nearby Olympia. In fact, detectives believe he went in the opposite direction.

"We have activity on his phone going down towards I-5 heading south," said Thurston County Sheriff's Detective Frank Frawley. "And then the phone starts heading back up north, and then it heads south again and stops where we've recovered the vehicle."

When the 19-year-old hadn't come home by Monday, his grandma filed a missing-person report. Police ran the license plates on Logan's car and discovered it had been impounded.

It all starts with three bizarre 911 calls. A car is drifting across lanes of a busy highway in Olympia, Washington -- but the callers notice something strange: There is no one in the vehicle.

"We found out the vehicle's been recovered already and then we get the story of some witnesses saying that they saw a subject running out from the vehicle, and for it to be abandoned on the interstate and hit the jersey-barrier, that's weird as well," said Det. Frawley. "One of the witnesses said the vehicle had veered towards the center lane and hit the barrier and stopped. Right in the middle of the highway."

It was a truck driver heading north on I-5, who claims he saw someone jump right out of the moving vehicle.

"He sees somebody jump out of the passenger side of the vehicle," said Frawley. "Initially he said a white male, but basically a male and then he ran towards the woods off the interstate."

Police searched a 2-mile radius of those woods by air and on the ground, but never found any sign of what might have been Logan.

One possible sighting of a naked teen later that night brings even more intrigue to the case.

"We thought that might have been Logan as well. And so they did initiate a search using dogs," said Frawley. "They didn't locate anything. Could've been Logan, could've been anybody."

Inside the teen's abandoned car, cops found Logan's wallet, identification and cellphone -- plus something that led to even more unanswered questions.

"One of the curious things was in the center console of the vehicle were some bags, like, grocery bags which kind of led us to believe that if somebody was on the driver side going over to the passenger side, those bags would have been knocked down," said Det. Frawley. "So there might have been two people and the truck driver only saw one person."

And they can't explain other strange occurrences either. An unexplainable digital clue in the case came one week after Logan vanished.

"He did a check-in on his Facebook page at the Olympia regional airport," said Frawley.

Nearly a year after he disappeared, there's been no sign of Logan Schiendelman.

"I have no reason to believe he's been killed. I have no reason to believe he's alive," said Det. Frawley.

Logan Schiendelman was raised by his grandmother in Tumwater, Washington. Logan returned home to live with his grandmother after just one year in college.

"He was kind of at a loss with what he was going to do with his life," said Logan's grandmother Ginnie Gebo.

And according to her, Logan started to smoke marijuana.

"I know he did a lot of smoking pot, and I've wondered sometimes if that caused a little bit of paranoia," said Gebo.

She believes her grandson was paranoid the morning he told her he'd had an epiphany. She told him they'd talk that afternoon, but they haven't since. Logan simply vanished.

The next day, his car was abandoned in the middle of Interstate 5. Detectives are even more perplexed after finding Logan's wallet, ID and cellphone inside his convertible.

If Logan didn't run away on his own, who would want to get rid of him?

"You have one part of the family saying there's somebody responsible, and the other side of the family that is saying nobody is responsible," said Detective Frank Frawley.

Logan's Uncle Mike Ware worked in law enforcement for years, and there was one person he thought detectives should investigate.

"If it were in the home, would be the tension and the hostility that's going on with his sister and her boyfriend," said Ware.

He claims when Logan returned from college, life at his grandmother's home had become very difficult.

"He was very upset about the boyfriend living in the home," said Ware.

Logan's half-sister had moved in her boyfriend, and according to the uncle, he and Logan didn't get along.

"They didn't particularly like each other, but they just kind of avoided each other," said Ginnie Gebo.

Det. Frawley questioned the live-in boyfriend, who agreed to take a polygraph test.

"I asked him if he was responsible for the disappearance of Logan. And I asked him if he knew who was responsible for the disappearance of Logan," said Frawley. "And he answered no to both questions, and my opinion was that he was not showing any deception when I asked those questions."

"Polygraphs aren't perfect. There's a possibility he could pass a polygraph somehow without being truthful," said Mike Ware.

Authorities have never charged the boyfriend in connection with Logan's disappearance.

Another theory detectives have considered is whether Logan's alleged drug use may have gotten him into trouble.

"We don't know if he maybe owed people money, or if he might have gotten some bad drugs or maybe does some other drugs," said Frawley.

But there's no evidence that a crime has even been committed.

"You know he can very well just be out there right now, wanting to be left alone," said Det. Frawley.

But why would Logan Schiendelman want to be left alone?

Logan's Aunt Tina Crary has a theory that only makes the mystery deepen further.

"Maybe he saw this as the only way to get out of this conflict, this dysfunctional family of his," said Tina Crary.

Before going away to college, Logan secretly met one side of his family for the very first time -- the black side.

Tina Crary says it was an emotional visit.

"I showed him a picture of his grandfather, my older brother, and he stared at it, he said 'It feels good to see someone that looks like me,'" said Crary.

She believes Logan was desperate to learn more about his background.

"He wanted some answers, and he wasn't getting them at home," said Crary.

Tina Crary claims Logan didn't want his grandmother, Ginnie Gebo, to know about their visit.

"He said 'If she finds out that I came here she's gonna be really mad,'" said Crary.

Crime Watch Daily asked Ginnie Gebo about that.

"I don't think that's true either," said Gebo. "They made no effort to get a hold of him and see him, and I had pretty much not talked to his grandfather in years and years and years, so there was just no connection. I wasn't actively trying to keep him away."

No one knows if Logan met up with a sinister fate, or if he is running from bitter family strife.

"He's welcome to come back any time without an explanation, and I think he knows that," said Mike Ware.

But until more clues surface, his family is left only with speculation -- and desperate pleas.

"If you don't want to be here, that's fine, but get a hold of us, let us know that you're OK," said Ginnie Gebo.

"If you need to stay away in order to feel secure, I wish you well and I send you off with love," said Tina Crary.

If you have information about Logan Schiendelman, contact the Thurston County Sheriff's Department at (360) 704-2740, or submit an anonymous tip to Crime Watch Daily.