Why Would Kids Want Their Stepfather Dead?

June 30, 2009 -- Nathan Gann, a clean-cut honors student who attended the University of Arizona, was a self-described computer geek. During the summer of 2007, 19-year-old Gann was busy blogging and posting videos of himself, which were goofy but showed a sense of promise and ambition, all over YouTube.

"I love the stars, ever since I was a child," he wrote on his MySpace page. "Because of them I have always wanted to reach for the stars. My dream goal is to be an astronaut."

Nathan's younger sister, 17-year old Brae Hansen, was equally driven. A high school honors student, who had recently returned from a church trip performing community service in Puerto Rico, she embraced life.

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But in July 2007, disaster struck. At first it looked like a home robbery gone wrong: Brae Hansen told the 911 operator that a masked intruder had shot her 63-year-old stepfather, Tim MacNeil, in their San Diego home.

But as police investigated the July 2007 shooting death, two unlikely suspects emerged -- MacNeil's own stepchildren.

Why would these teens want their stepfather dead? The evidence didn't seem to add up. Brae reportedly adored her stepfather, whom relatives said she always affectionately called "Daddy."

Tim MacNeil had met and married their mother, Doreen Hansen, a schoolteacher, when Nathan and Brae were 7 and 5 years old. Erin MacNeil, Tim MacNeil's daughter from a previous marriage, told ABC News' Mary Fulginiti that Brae and Nathan were part of the family.

"They were his kids," she said. "He treated them just like any other ... just like he treated me."

However, Brae and Nathan were two kids who had spent their lives desperately trying to earn their mother's love.

Family court papers revealed that Doreen Hansen was suicidal, depressed and had been abusing both her children from an early age. For Nathan, it seemed to be an especially torturous upbringing.

"She was physically violent with him, hitting him ... with sticks," claimed Nathan Gann's attorney, Ricardo Garcia. She would, ridicule him. He would be in the bathroom ... and [she would] bring his sister in and point out his penis and ridicule him about it in front of his sister."