OTTAWA - Canadian prison service officials could not have prevented an inmate who was let out of jail from carrying out the country's worst ever mass stabbing, an official report said on Tuesday.

Myles Sanderson, 30, was released with conditions in February 2022 after serving time on charges of assault and robbery. In early September 2022, he killed 11 people and injured 17 in attacks across 13 sites in the western province of Saskatchewan, and died of a cocaine overdose shortly after being arrested.

Authorities had issued an arrest warrant for him in May 2022 when he failed to make required contact with his parole officer. Federal inmates are eligible for automatic statutory release under supervision after serving two-thirds of their sentence.

A 162-page report into his release, carried out by the Correctional Service of Canada (CSC) and the Parole Board of Canada (PBC), said the preparation had been reasonable and appropriate and carried out by qualified staff.

The investigation "concluded that there were no pre-indicators or precipitating events that were known to CSC and PBC staff, or that staff could have acted upon to prevent this incident," the two organizations said in a news release.

The report noted Sanderson had a lengthy criminal history and a propensity for violence, including towards his common-law partner. Staff were attempting to address these issues through a special plan designed to correct his behavior.

The stabbing spree rattled a country unaccustomed to acts of mass violence and raised questions about violence, trauma and substance use prevention and policing in remote and Indigenous communities that are frequently marginalized.

CSC Commissioner Anne Kelly said in a separate statement that the service would review its procedures for locating offenders who were unlawfully at large. REUTERS