Toronto police Staff Insp. Mike Earl said the 37-year-old guard was "ambushed" by three males as the Garda World security truck pulled up to service a TD Bank branch (in the Avenue Road and Lawrence Avenue area).
"There were numerous shots fired in this incident that lasted approximately less than a minute — 40 seconds, 45 seconds," said Earl.
He said the number of shots fired was "in the double digits."
Earl said the guard, who returned fire, took four rounds to the body and was undergoing surgery.
He said a second guard never got out of the truck — which went into lockdown — and the suspects fled on foot.
Three men, all 18 years old, were later arrested and are facing multiple charges, including attempted murder.
Police allege the same three suspects also attempted to rob a Garda World truck operated by the same pair of guards in the same area on June 5, also in the early morning hours.
"It happens to be that it's the same victims in this case that were targeted," said Earl.
"These individuals no doubt planned this and attempted this on an earlier date," he alleged. "And today they tried and made a similar attempt which resulted in a shootout."
But he said there's no indication the shooters were looking for these particular guards.
"I don't think the two individuals, the two victims, are specifically targeted — it's the actual truck or the company that's being targeted," he said.
Earl said a handgun was seized during the arrests and no other suspects are being sought. He said none of those arrested was previously known to police.
In addition to the attempted murder charges, Jaden Beckford, Nicholas Cross and Rashid Clarke are each charged with two counts of armed robbery, two counts of conspiracy, two counts of wearing a disguise with intent and seven firearms-related offences.