Parents of Ryan Sims, a 23-year-old Brown University graduate whose dismembered remains were mysteriously found in a subway tunnel last December, have filed a lawsuit against the Metropolitan Transportation Authority seeking access to surveillance footage that could reveal the actual cause of his death.

His parents want to see the video and other possible photographs to track his movements and determine if MTA track cleaners ran over his body, or moved his remains after he was dead.

Sims' body was spotted by a train conductor, Dec.11, around 7:15 a.m. on the tracks under a tunnel between New York's First Avenue and East 14th Street subway stations.

Police suspect that he might have been fatally struck by a Manhattan-bound L train.

His last known location was Eighth Avenue L station, where Sims used his Metro Card around 7:00 p.m. Dec.10.

The investigation has not yet concluded the cause of his death, which could be an accident, foul play or suicide. However, a medical examiner revealed that Sims' death occurred due to a blunt-force trauma after being struck by one or two trains.

The lawsuit filed at Manhattan Supreme Court, Wednesday, also states that Sims' personal belongings such as iPhone, wallet, backpack and eyeglasses, have not yet been found.

Agreeing with Sims' parents, his friends also do not believe that he committed suicide.

"I really wonder if it was foul play. He's extremely trusting, such a beautiful soul. He always had the best perspective on everything, and suicide doesn't seem likely to me at all," Sara David, his college roommate, told the Daily News. "He was one of those kids that was good at everything."