BOISE - An autopsy revealed 45-year-old Dennis Lewis died from a gunshot wound to the back of the head.

His 17-year-old son Derek was arrested in Oregon after evading police in a high speed chase. He's charged with first degree murder. Family members say they're in shock.

Kasey Broyles, Derek's cousin, is one of those relatives in mourning.

"I just can't believe it, just can't believe it," Broyles said. "I was in their wedding, so I had known him since I was really young and he was just a kind hearted guy."

Broyles said Dennis meant the world to Derek and she can't imagine why this would happen.

"Dennis was a great father to him, he looked up to him, Dennis did everything he could for him, he was a great dad," she said

Derek's parents divorced when he was a baby, but his mother, Molly Tripp, says they've stayed friends. She says there was never any violence between father and son. Tripp says over the past few years Derek has suffered from a medical condition that changed his overall demeanor. He was diagnosed with Ulcerative Colitis in 2005 and had his colon removed. Tripp says her son went from being an outgoing, athletic teen, to wearing colostomy bags and dropping 30 pounds.

Family member say not only was he ashamed, his sports career was over. They say his dream of serving in the military was crushed.

"He's a trooper, he's gone through a lot than more kids at his age should have with illness and he's hung on," Broyles said.

The shooting happened at Dennis' Boise home where Derek spent some of his time. He was in and out of school and most recently attended Fort Boise, but only for five days this year. Derek's mother says he left school to earn his GED. She says she doesn't have any idea why Dennis was murdered or how her son turned out to be the suspect.

Relatives say they feel like they've lost two loved ones, though only one will be buried.

"Family sticks together, but with God's strength we're making it," Broyles said.