Edmonton - A troubled 15-year-old shot and killed relatives who had taken him in because his mother could not control him, then stole their car and fled with the younger girlfriend they had ordered him not to see, police and family members said.

Gary and Barbara Holloway's adult son found them dead in their bed Tuesday. Police issued an Amber Alert for the teen and his 12-year-old girlfriend, saying they feared they might be in grave danger. They soon caught up to them after a volunteer firefighter spotted them in the car, the 15-year-old behind the wheel.

By Wednesday, in one of the strangest cases to arise from the system designed to find abducted children, the teen had been charged with murder in the Holloways' deaths.

Family members said the boy was an eighth-grader at the local middle school who habitually got in trouble for bringing cigarettes to school, bullying other children, and talking back to his teachers.

Barbara Holloway, his second cousin, had taken him in three months ago, said her sister, Ruby Whitehead. Family members said his father is in prison.

"He's always been abandoned his whole life," said Elizabeth Osborn, a friend of the Holloway's son, Stephen. "... I guess the first people who showed him love, he didn't know how to take it."