The 24-year-old, who played Jeffery Augustine in the teen drama Riverdale, was sentenced at British Columbia Supreme Court in Vancouver.

Grantham turned himself to police soon after shooting his 64-year-old mother Barbara Waite in the back of the head on March 31, 2020, in the family’s Squamish home, just north of Vancouver.

The court also heard Grantham had considered committing an act of mass violence at Vancouver's Lions Gate Bridge or at Simon Fraser University, where he had been a student, en route before turning his car around and handing himself in.

During the trial, his lawyers argued he had been struggling with anxiety and clinical depression and had expressed a desire to kill himself and harm others in the months leading up to him killing his mother.

He will not be eligible for parole for the first 14 years of his life sentence.