An Edmonton man who viciously attacked a city bus driver read a letter at the conclusion of his dangerous offender hearing admitting responsibility and blaming alcohol.

Gary Edwin Mattson pleaded guilty in May 2010 to aggravated assault for attacking Tom Bregg on his bus during the morning rush hour on Dec. 3, 2009.

Gary Mattson is shown here on a bus security video moments before he attacked Tom Bregg on Dec. 3, 2009. Edmonton Transit The Crown is now seeking to have Mattson declared a dangerous offender and kept in prison indefinitely.

In the letter Mattson read Monday, he takes full responsibility for beating Bregg and stomping on his face 15 times. The attack put Bregg in intensive care for two weeks and left him blind in one eye.

Mattson called himself "a terrible drinker" and said "I underestimated the alcohol in me" at the time of the attack.

Crown prosecutor Patricia Innes said despite the comments, Mattson should be declared a dangerous offender.

Tom Bregg spoke to reporters in Ottawa last March when Edmonton Conservative MP Brent Rathgeber introduced legislation to increase sentences for people convicted of assaulting transit operators. CBCShe said Mattson needs a "stable lifestyle imposed on him."

The attack, which put Bregg in intensive care for two weeks and left him blind in one eye, was caught on the bus security camera.

Mattson's dangerous offender hearing started in December and has continued intermittently over the past seven months.