Then he picked up a knife and stabbed his nine-year-old brother and slashed his sister, five a number of times, leaving a trail of bloody destruction.
The news shocked the small community of Burlington, CO, who described the family who ran their own church and home schooled their kids as deeply religious.
To this day the boy, who is now 13, has never explained, why he committed such a heinous crime. District Attorney Bob Watson told the court: "If you're looking for an adult explanation for why this kid went from playing in dirt to commit murder you'll never get one.
"This lies in the mind of a very immature 12-year-old."
He added that state law forced him to choose between what he saw as an unacceptably light juvenile sentence and an unnecessarily harsh lifetime sentence.
His brother, Wally Long, said he was never in favor of a plea agreement.
He told the court that his brother was "dead to me" adding: "My desire for a longer sentence was never about hatred or anger but out of a sense of justice."