Ryan Jordan Gibson, who pleaded guilty to killing a 17-year-old while driving drunk, has been sentenced to two years and eight months in prison.

The 24-year-old admitted in January to driving head on into Brandon Thomas' Subaru.

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Brandon Thomas, 17, died in December 2012 when a drunk driver on Highway 22 near Cochrane smashed into his car. (Submitted by Thomas family)

Brandon's mother Kim Thomas said there should not have been a plea bargain. She was hoping for a longer sentence.

"He's the person that ruined my life and the rest of our future together. All the things on a daily basis that I know we'd be doing as a family, we don't do. Brandon's graduation is coming up at the end of this month — how do I do that?" she said.

"I always was against the two-year sentence. I knew that was a possibility. I begged the Crown prosecutor to fight for Brandon to fight for innocent victims and their families and at least the judge did that for us."

Thomas said she will continue on with her work with Families for Justice to lobby for stiffer sentences.

According to an agreed statement of facts, Gibson had been visiting friends in Cochrane in December 2012 when he passed two semi-trailers but stayed in the oncoming lane for a period of time and sideswiped two cars.

One car ended up in a ditch and the passengers sustained no injuries.

However, the other car rolled several times before landing in a ditch and resulted in some injuries.

Gibson then collided head-on with a third vehicle, and Thomas died at the scene.

Judge Karim Jivraj said the case is a sad, but all too frequent example of what can happen when people choose to drink and drive.

"But for this one grave error in judgment…[Gibson] appears to have led an exemplary life which would make any parent proud," he said.

The judge offered his condolences to Thomas' friends and family. 

"To characterize Brandon's death as tragic would be an understatement," he said.