Prior to the collision, the controller-in-charge was coordinating multiple issues, which included communicating with firefighting crews on the ground, the report said.The local controller took over transmitting air traffic instructions on both ground control and local controller frequencies at this time, according to the report.Air Canada’s pilots were given clearance to land by the tower about 21 seconds before firefighting crews left the airport’s fire station area to respond to an emergency. The lead truck attempted to contact the tower 40 seconds after the plane was given clearance to ask to cross the runway, but a simultaneous transmission obscured the call.A second attempt to reach the the tower was made 34 seconds later. The team in another truck, identified as Truck 1, moved to the front of the convoy of responders to wait at the taxiway intersection.The trucks were given clearance to drive across the runway, and began to do so less than 30 seconds before the crash. They were instructed to stop for the first time about 20 seconds before the collision, according to the report.In an interview with investigators, one of the Truck 1 crew members said he heard the words “stop stop stop” on the radio but did not know whom the order was for. He only realized after a second transmission came through that said, “Truck 1 stop stop stop,” but it had already entered the runway.“He further recalled that as they turned left, he saw the airplane’s lights on the runway,” the report said.