LOVELAND, Colo. -- The stepfather of two teenagers killed in a crash earlier this year pleaded guilty Friday to beating to death the driver who caused the crash.

Phillip Chavez, who had faced a charge of second-degree murder, pleaded guilty to a charge of reckless manslaughter, the Adam's County District Attorney's Office said.

On March 8, Chavez was returning from a Nuggets game with his son and daughter when they pulled over on Interstate 25 in Northglenn and were rear-ended by 62-year-old Glenn Ryburn.

Damien Noyes, 14, and 13-year-old Angel Noyes, both of Loveland, were killed instantly. They were sitting in the back seat of the Ford Escort, which was crushed by Ryburn's Chevrolet Blazer.

Chavez attacked Ryburn while he was still buckled in his car, clobbering him repeatedly, according to police at the scene. One witness said that Chavez hit Ryburn approximately 150 times, prosecutors said.

Ryburn never regained consciousness after the crash and died May 16. The coroner ruled that his death was the result of blunt force trauma to his head.

Both men were intoxicated, prosecutors said.

Damien was an eighth-grader and Angel a seventh-grader at Conrad Ball Middle School.

If the judge finds extraordinary circumstances, Chavez could face up to 12 years in prison when he is sentenced on Jan. 30.