You never leave a brother behind.

That is why Yuriy Bekhenik, a Massachusetts state trooper, says he is determined to help solve the 25-year-old cold case murder of fellow Marine David Cox, who was involved in a hazing incident that inspired the movie “A Few Good Men.”

“It’s one of those things: never leave a brother behind. I feel like David has been left behind for 25 years,” Bekhenik said in an interview with WFXT, a Fox affiliate station.

Bekhenik is working with another former Marine, John Fanning, a sergeant with the Massachusetts State Police, to find out who killed Cox in 1994, when a canoeist on the Charles River found the body of the then-27-year-old Marine.

The canoeist had become curious about a sneaker sticking out of a pile of branches in a nearby woods and got out for a closer look. When he moved the branches, he found Cox's body.

Cox, who had been missing for about four months, had four shot wounds – one on the back of the head and three on his side.

The former Marines have enlisted the aid of forensic experts.

For several reasons, they suspect that Cox trusted whomever did him harm, WFXT reported.

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They maintain, for instance, that former Marines typically avoid wearing their uniforms in public, but Cox wore his on that day.

“David wore that field jacket and his Marine Corps sniper jacket for a reason that day, “ Fanning said. “David knew who he was going with, he trusted that person.”

Cox for some reason went out to the woods wearing only sneakers, despite a snowstorm that had hit the area the night before, dumping about 8 inches on the ground.

Cox went for drinks with his brother, Steven, the night before. Steven Cox was quoted as telling the news station that his brother seemed less outgoing than usual, but that he knew of no problems other than some tensions with his live-in girlfriend. His girlfriend saw Cox the morning of his last day alive, just before she left for work.

There were signs that someone gave Cox a ride to the woods where his body was found.

Theories for what may have happened to Cox abound, though Bekhenik and Fanning outright dismiss several of them.

One of the theories has to do with the movie, “A Few Good Men,” based on a serious hazing incident involving Cox and 10 other Marines.

The incident led to courts martial, though Cox challenged his and won, which enabled him to get an honorable discharge. The movie took some liberties, among them having the Marine who was hazed die. In reality, Cox and some other Marines helped save the colleague who was hazed. Cox was vocal about his disappointment in the way that the movie portrayed the incident, and threatened a lawsuit. But he died before he could take action, raising questions among some – including Cox’s brother, Steven, according to WFXT -- about whether there might have been a connection to the dispute and his murder.

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The Massachusetts police say they investigated that angle, but came up with no evidence to support it.

Cox’s sister, Christine, believes it was well-planned and not the work of an amateur, but she discounts the Hollywood or Marines connection.

She thinks someone her brother knew and perhaps trusted had him walk nearly a mile into the woods, where they shot him.

"We were pretty close. Outside of losing a brother, I lost one of my best friends, " Steven Cox said.

His sister added: “David’s life mattered. He was erased. This person erased his life, his future. I want the killer identified. Not to us, to the world. I want everybody to know who did it. I want him to pay for it.”