Edmonton Transit driver Tom Bregg leaves the courthouse on Thursday. (CBC)

Edmonton Transit employees packed a courtroom Thursday to hear a man plead guilty to aggravated assault in the vicious attack on veteran bus driver Tom Bregg last December.

Gary Edwin Mattson, 25, was originally charged with attempted murder and aggravated assault after the attack during the morning rush hour on Dec. 3. Mattson didn't enter a guilty plea on the attempted murder charge.

Bregg suffered life-threatening head and facial injuries in the attack. He chatted with colleagues outside court, a shut left eye serving as a reminder of the severity of his injuries, five months after the attack.

Later Thursday morning, Bregg walked into court to hear statements from witnesses.

Dispute arose over fare

Bregg was driving the No. 10 bus at 7:30 a.m. that day when he stopped to pick up a man at 139th Avenue and Victoria Trail in northeast Edmonton.

Mattson refused to pay the fare when he got on the bus. He started swearing at Bregg and, according to witnesses, punched him and pulled him out of his seat after being asked to leave.

Mattson then dragged Bregg onto the sidewalk and "stomped on his face," the court was told.

According to a police report presented in court, Mattson appeared moderately drunk at the time and was belligerent. He spat at one of the arresting officers, the report said.

Bregg was in intensive care for more than two weeks after the attack. He also needed rehabilitation at Glenrose Hospital.

Bus driver Charlene Logan, one of the Edmonton Transit employees in court, said she saw some of the photos of the December attack.

"Being in the front row, I could see over the shoulder, and it was pretty harsh, pretty harsh stuff," Logan said in an interview.

"It was sad, it was really sad … you keep thinking it could be anyone of us."

Crown prosecutor Pat Innes told the court she intends to ask the court to designate Mattson a dangerous offender.

The matter was adjourned Thursday afternoon. A date for sentencing has not been determined.

Innes said the Crown would deal with the attempted murder charge after the sentencing for aggravated assault.