<(WBIR- Knoxville) It's been more than five years since a Wisconsin man was found murdered in a Knoxville home, but detectives said they are continuing to crack leads in the cold case.Jerry Barrett, 35, came to Knoxville for a job to lay tile, but was trying to move back home before he was shot in the head on February 17th, 2008. "It destroys your life. You're heartbroken at first, and then you get angry, and your mind never shuts down," said Craig Barrett, Jerry's father. "You're looking for closure, and it never comes. You're waiting for an answer and it's just ongoing, 24 hours a day."Early Sunday morning, Barrett got the call that's a father's worst nightmare."A friend of his called me and said there was an accident down there. And I thought an auto accident or something, and then they told me no, he was murdered. Shot in the head," recalled Barrett.Detectives said the homeowner on Wayne Street was not there, and a witness was left unharmed, handcuffed to the front porch."I would say, yeah, suspicious," said Jeff Day, with Knoxville Police Department's Cold Case Division. Day said there was drug activity at the house, and the killer left behind a huge stash of marijuana."There was a lot of it here, I can tell you that," said Day."That's the suspicious part. Is that, they didn't take that, for some reason. So there's something else involved," said Barrett.Jerry, who went by Jay, got sick from Legionaries Disease, a type of pneumonia caused by bacteria. Barrett said that's when his son started hanging out with the wrong crowd."The hospital put him on oxycontin for about nine months and then cut him off. And it's the same old story. You get strung out on the stuff and then you're hung out to dry," said Barrett. "So we tried to get him help, and he was actually coming home. He had come home for Christmas and he was getting ready to pack up and come back."Five years later, detectives said they are still following leads and interviewing people, including the handcuffed witness."He's talked to us a few times, but we're not done talking to him," said Day.Solving this murder could also mean getting a drug dealer off the streets."Any information that we get from the public that would help us solve the murder could also help with the prosecution of a drug ring, or it could be tied together," said Day. "It just doesn't make sense that you would go into a place, you wouldn't rob it, you tear it up a little bit, put handcuffs on one person with the keys there and ties on my son and shoot him the head for no reason," said Barrett.Anyone with information on the case is asked to call 865-215-7015. Details could help detectives close the cold case and put the killer behind bars.<