SUMMIT COUNTY, Colo. (CBS4) – Video became a key piece of evidence in a criminal trial of a man facing prison time after driving head-on into a bus with his girlfriend in the passenger seat.

Prosecutors say Joshua Pierce was trying to kill his girlfriend.

The collision jarred passengers on a Summit County public bus last May and left Pierce’s girlfriend severely injured. Pierce can be seen in bus surveillance video running from his car right after impact.

Pierce appeared in court Monday to plead guilty to lesser charges.

“One is vehicular assault under a theory he was driving the vehicle in a reckless manner and that that conduct was the result in serious bodily injury to another person,” Pierce’s attroney said.

Pierce avoided a charge of attempted murder. He had told police he was fighting with his girlfriend while they were driving.

In court his attorney said he hadn’t slept for a week, and that’s what led to the high-speed collision. Transit officials said the bus was forced back five feet and racked up nearly $3,000 in damage.

“Those are two children on the bus that were injured as a result of the defendant’s conduct,” the prosecutor said, referring to video of the passengers.

Pierce’s attorney said the act was not intentional.

“He is accepting a plea based on a reckless theory on all three counts,” he said.

Pierce will be back in court in March for sentencing.