OpenAI said it identified the account of Jesse Van Rootselaar months before a deadly school attack in British Columbia.
Its systems flagged the activity in June for the “furtherance of violent activities”.
The company reviewed whether to alert the Royal Canadian Mounted Police.
It decided the case did not meet its threshold for referral.
That threshold requires a credible and imminent risk of serious harm.
Van Rootselaar later killed eight people in Tumbler Ridge before taking their own life.
Police said the victims included a teaching assistant and several students.
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 will continue to assist the investigation.
The motive remains unclear.
The attack is the deadliest in Canada since the 2020 Nova Scotia killings.
