(NewsNation) — The family of 22-year-old Riley Strain believes someone helped the University of Missouri student into the river where his body was discovered weeks after he went missing in Nashville, Tennessee.

Strain’s family spoke with NewsNation senior national correspondent Brian Entin, saying they haven’t seen convincing evidence Strain fell in by accident.

Riley Strain’s family talked to NewsNation’s Brian Entin about Riley’s fraternity brothers, his messages about his drink and more in an extended exclusive interview. Not sure how to watch NewsNation? Log in to this web player or go to JoinNN.com to locate us on your TV. 

“If he truly fell in the water, and you can prove that to me, show me,” his stepfather, Chris Whiteid, said. “I’ll accept it. But I can tell you from all the stuff that we’ve done as far as searching, looking, taking pictures — I don’t feel like it’s really possible to happen. He may have fallen. Somebody helped him in the water.”

Strain’s body was found March 22 in the Cumberland River in West Nashville. Police said the college student’s death appears “accidental,” with no trauma suggesting foul play, according to preliminary autopsy results.

The medical examiner who performed that autopsy said there was no water in Strain’s lungs. That detail, along with a lack of cuts and bruises on Strain’s body and the inclined terrain where Strain is believed to have fallen from, has only made the young man’s death harder to piece together, his family said.

His stepfather believes Strain would have hit his head or suffered other injuries if he had fallen straight down into the water.

“No cuts or scrapes or anything serious like that,” Whiteid said.

The family has ordered a second autopsy that they hope brings clarity.

Strain disappeared March 8 during a trip to Nashville with his Delta Chi fraternity brothers.

Earlier that night, Strain messaged his mother, Michelle Whiteid, saying he ordered a rum and Coke that “didn’t taste good.”

The TC Restaurant Group, which owns and operates the bar, said Strain was asked to leave after being served one alcoholic drink and two waters.

His toxicology results aren’t complete yet. It’s unclear what else, if anything, may have been in Strain’s system at the time.

He communicated with his mom throughout the trip and texted her when they arrived at the hotel, she said. The next morning, when Whiteid woke up to go grocery shopping, she received a call from his fraternity brother, asking if she’d heard from Strain.

Michelle and Chris Whiteid quickly headed from Springfield, Missouri, to Tennessee. Ryan Gilbert, Strain’s father, said he also made a seven-hour trip down there.

When the family arrived in Nashville, Strain’s frat brothers “all of a sudden disappeared, all of the boys,” during the search. “A little later,” they showed up “in their dress clothes to go out to their formal that night,” Michelle Whiteid said. 

His body was discovered two weeks later, about 8 miles from where he was last seen. Strain was missing his wallet, pants and boots. Strain’s family said he had been wearing a belt that night, which should have secured his pants.

Forensic pathologist Priya Banerjee and NewsNation law and justice contributor Jennifer Coffindaffer previously told NewsNation it’s difficult to make the “leap” that something “nefarious” happened to Strain.

“Eight miles is really long undercurrent,” Banerjee said. ”I think you could lose things.”

Chris Whiteid says he wants to know what happened and that he will continue to look for answers.

“If he fell and truly fell in the water, and you can prove that to me, show me. I’ll accept it,” he said to NewsNation. “But I can tell you from all the stuff that we’ve done as far as search and looking, taking pictures — I don’t feel like it’s really possible that happened. He may have fallen, but someone helped him in the water.”