Ryan Grantham, a young Canadian actor who appeared in the television show “Riverdale,” has been sentenced to life in prison after admitting to killing his mother as part of a broad scheme in which he said he had planned to also kill Prime Minister Justin Trudeau and carry out a mass shooting in British Columbia.

Grantham, 23, was declared eligible for parole after 14 years during sentencing proceedings at the Supreme Court of British Columbia on Wednesday, according to prosectors and a lawyer for Grantham.

Grantham had pleaded guilty earlier this year to second-degree murder, which carries an automatic sentence of life in prison. The main issue at the sentencing was when he would be eligible for parole. Prosecutors had called for a 17- to 18-year waiting period before Grantham could apply for parole, Grantham’s lawyer had asked for a period of 12 years, and a judge on Wednesday chose a number in between.

The court also imposed a lifetime firearm ban on Grantham, prosecutors said.

Grantham has more than 30 acting credits, starting when he was a child. He appeared in the 2010 movie “Diary of a Wimpy Kid,” in which he played Rodney James, and in several other films, including “The Imaginarium of Doctor Parnassus.” Most recently he played the character Jeffery in a 2019 episode of “Riverdale,” a dark reimagining of the Archie Comics franchise on CW.

His lawyer, Chris Johnson, said that Grantham had suffered from a number of documented mental health challenges including clinical depression and that, since entering prison, he had “committed himself to trying to rehabilitate himself.”

The crime occurred on March 31, 2020, when Grantham, then 21, shot his mother, Barbara Waite, in the back of her head as she played piano in their home in Squamish, a town in British Columbia about 37 miles south of Whistler, Johnson said. Grantham recorded a video shortly after that in which he confessed to the murder and then left by car, Johnson said. Grantham told the authorities that he initially had planned to kill the prime minister, but changed his mind and at some point decided he would carry out a mass shooting, possibly at Simon Fraser University, where he had been a student.

He did not carry out either plan, and instead turned himself in to the police on April 1, 2020, Johnson said.

Grantham had rationalized that it was necessary to kill his mother so that she would not have to deal with the fallout of the crimes he had planned to commit, Johnson said.

Susan Beachy contributed research.