OpenAI considered notifying the Royal Canadian Mounted Police about a user later responsible for a deadly school attack.
The company flagged the account in June for activity linked to the furtherance of violence.
At the time, it decided the case did not meet the threshold for referral.
Its policy requires evidence of a credible and imminent risk of serious harm.
The firm said it found no sign of immediate planning.
The suspect, Jesse Van Rootselaar, killed eight people in British Columbia before taking their own life.
Police said the victims included a teaching assistant and five students aged 12 to 13.
The attacker had previous mental-health-related contact with authorities.
After the shooting, OpenAI contacted the RCMP and shared information about the account.
The company said it would continue to assist investigators.
The motive for the attack remains unclear.
The violence in the small town of Tumbler Ridge is Canada’s deadliest mass killing since 2020.
