For as many as 40 nerve-wracking minutes last September, Montreal police believed the Dawson College shooting was part of a co-ordinated terrorist attack on the city.

There were false reports of gunfire at four different downtown locations, the Montreal police commander on the scene told a conference on emergency preparedness on Tuesday.

Mario Plante, assistant director of the Montreal police, said he was faced with four erroneous reports when he arrived on the scene.

An early report said officers had shot one gunman, but that there were other armed suspects who had taken hostages on upper floors of the building.

Some officers also reported hearing what they thought to be shots being fired in their direction from upper floors.

One citizen reported shootings at two nearby hospitals while another said a gunman dressed in combat fatigue pants was firing at a nearby shopping and office complex.

As it turned out, "there was only one shooter," who was shot dead by one of the first police officers on the scene.

It took eight hours before police were able to sift through the incorrect reports and conclude that it had been a lone gunman.

Kimveer Gill, 25, was shot dead by police after he went on a shooting rampage, injuring 20 students and murdering 18-year-old Anastasia De Sousa.

Retired Montreal homicide detective Stephen Roberts says he was not surprised to hear police initially feared the shooting was a terror attack.

"You have to remember there were gunshots inside of a building. These gunshots echo all over the place and this was one point so if somebody was up on the third or fourth floor, they would think the gunshots were coming from up there," he told CTV's Canada AM.

The near-simultaneous collapse of the mobile communications network further complicated the situation as senior officers who arrived on the scene found their phones didn't work.

While some officers used walkie-talkies, others set up a command post using land phone lines.

"They're going to have to look into another way of communication, maybe by looking at satellite phones," Roberts said.

Meanwhile, investigators have found evidence the gunman may have scouted other potential targets -- high schools in the Montreal suburb of Laval -- before he zeroed in on Dawson, according to reports.

Plante says lives were likely saved at the school because of lessons learned from the �cole Polytechnique de Montr�al massacre of 14 female students in 1989.

Montreal police say false reports of terror attacks have shot up after the arrest of 17 people suspected of plotting acts of terrorism last June in southern Ontario.