He's not a crime fighter, but he does play one on TV. You probably remember Dylan McDermott from roles on hit TV shows like The Practice and Dark Blue, but this star's glitzy life also has a hidden dark side.

When McDermott was just five years old, his mother died under mysterious circumstances. Questions surrounding what really happened to her haunted the actor for the rest of his life, and he eventually helped solve a real life cold case four decades in the making.

The Murder

Dylan's mother was named Diane McDermott. She became pregnant with Dylan as a teenager, and separated from his biological father soon afterwards. Dylan and his infant sister Robin moved in with Diane's new boyfriend, named John Sponza.

Sponza had a reputation for being violent and abusive towards both Diane and Dylan. So it wasn't unusual when he kicked five-year-old Dylan out of the house one night, leaving him in the freezing cold.

Soon, Dylan heard yelling and a gunshot from inside the house. Then, an ambulance arrived and took his mother away on a stretcher, with a massive head wound. Sponza told police that she had shot herself by accident by picking up a gun he was cleaning.

But that story didn't sit right with McDermott. Years later, he helped uncover the truth...

Soon after Diane McDermott's death, Sponza changed his story, claiming that she had committed suicide.

The Cold Case

Suicide remained Diane's cause of death until 2011, when McDermott, now a successful and famous Hollywood actor, asked the police department in his hometown of Waterbury, Connecticut to re-open Diane's case. Investigators dug into old press clippings and re-interviewed sources from 1967, and what they uncovered was shocking.

Detectives identified a glaring inconsistency that had been missed in the original case: Diane's head wound was on the left side, while she was right handed. Other incriminating details about Sponza also came to light: He was a bank robber and a violent criminal with ties to organized crime.

The Killer

Police say Sponza avoided serious jail time only because his father ran the local prison. Other sources revealed he might have been a police informant, and the detective in charge of Diane's case was mysteriously fired years after the murder.

Looking back, it seems like an open and shut case against Sponza, but justice couldn't be served. Sponza's criminal past caught up with him in 1972, and he was found dead in the trunk of a car parked outside a grocery store.

Sponza might have escaped justice for Diane McDermott's murder, but solving his mother's case gave the actor the closure he had been seeking for four decades.

"I've come to the point in my life where I'm able to begin to process all of this," he reportedly told police.

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[H/T: Daily Mail]