(CNN) Canadian police officials said on Wednesday that they failed to issue a timely public alert about the gunman responsible for the Nova Scotia shooting rampage last weekend that left 22 dead.

The Royal Canadian Mounted Police said officers were informed by a witness on Sunday, between 7 a.m. and 8 a.m., that the gunman was likely driving a lookalike police car and wearing an RCMP uniform.

At that point, police said they started the process of issuing an alert but it took several hours to make its way up the chain of command. Nearly three hours later, an alert had still not been issued.

"Nova Scotia emergency management officials contacted the RCMP to offer the use of the public emergency alerting system," RCMP Chief Superintendent Chris Leather said during a press conference Wednesday. "We were in the process of preparing an alert when the gunman was shot and killed by the RCMP."

The gunman, Gabriel Wortman, led police on a miles-long, 12-hour manhunt across the Canadian province. He died after a confrontation with police, the RCMP said.

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