Two men are dead after an altercation led to a security guard opening fire at a McDonald's restaurant in Toronto's east end early Saturday.

Det. Sgt. Terry Browne told reporters that the shooting occurred after an armed and uniformed security guard became involved in a "fairly significant physical confrontation" with two other patrons at the fast-food restaurant at about 3 a.m. Saturday.

The two patrons appeared to know each other, he said.

One was later identified by family as Donny Ouimette, 25.

The other man is believed to be age 40.

The guard was transported to hospital to be treated for an injury to his hand, and is co-operating with officers as they continue their investigation.

The guard did not work for the restaurant, located in the Coxwell and Danforth area, but was picking up food at the time of the incident. Browne said there were up to 20 other people in the restaurant at the time of the shooting, including customers and staff.

The incident happened in the area where people line up to buy food, police said.

Browne said no arrests have been made in connection with the incident, and police are looking to speak to anyone who may have witnessed the shooting.

He said it was not immediately clear why the altercation started, but officers are reviewing surveillance video from the restaurant as they continue their investigation.

"From what I see on the video, it started very quickly and escalated from there, obviously," he said. "There's no doubt that the security guard is the involved party for the discharging of the firearm. We're really trying to put the pieces together for how this all played out and where we go from here."

Anyone who has any information about the case is being asked to contact police.

The lawyer for a security guard involved in the fatal shooting of two men at an east-end Toronto McDonald's early Saturday says the gun that was involved was "lawfully possessed."

On Sunday, the lawyer for the security guard involved said his client’s gun was “lawfully possessed.”

With a report from CTV Toronto’s Scott Lightfoot