You could call him 'The Knock-Knock Killer" because a knock on the door was one of the last sounds Jimmy Driscoll heard before someone pulled the trigger and took his life on June 28, 2010.

Friends gathered at the home of Driscoll's girlfriend on North Main Street to watch television and hang out. Apparently they were having a good time when a stranger came calling.

"There had been a knock at the door. The side door," said Sgt. Bill Ashton of Memphis Police. "Jimmy goes to the side door, opens it up. No words exchanged, just a volley of gunfire."

Driscoll is shot and dies at the hospital.  

"All the family, friends we talked too, no one can came up with a reason," Sgt. Ashton said. "Jimmy was not into it with anybody, had not had any dealings with anyone that would raise any suspicion."

The gunman fled before anyone could get a good luck at his face. Detectives believe the getaway car might have been an older Chevy Impala seen driving in the neighborhood. It looked so suspicious that neighbors called police before the shooting.

Other than the car, the clues are few.

"Hopefully when this airs on TV it will shake something in someone's memory - 'That I heard so and so talk about this,' 'let me call the police and give them this information.' That is what I am looking for," Sgt. Ashton said.

If you can assist police you are urged to call Crime Stopper at 901-528-CASH. You anonymous tip could lead to a cash reward in this cold case.