Two people were injured, including a bystander, after a shooting outside a Mr. Sub restaurant on Macleod Trail on Saturday.

Witness Peter Mo was enjoying lunch at Pho Chu The at 4633 Macleod Trail S.W. when he saw an altercation break out between a group of men.

"The three of them went outside … and then he took his gun out and he shot him," Mo said.

"There were like four bangs that went off and everybody just started ducking to the ground."

Mo said he took cover before calling police.

Police said they received multiple reports of gunshots shortly after 1 p.m. Saturday, when occupants of two vehicles fired shots at each other.

Police investigate a shooting outside a restaurant on Macleod Trail on Saturday. (Helen Pike/CBC)

"Some of the rounds unfortunately went into the Mr. Sub," said Detective Shawn Rupchan with Calgary police.

At least one bullet smashed through the window of the sandwich shop across the street, catching a patron of the business in the crossfire.

"The poor customer at the [Mr. Sub] restaurant is very lucky in one sense that the bullet just missed hitting him directly," Rupchan said. "But he still sustained life-altering injury from the glass shattering [into] his eye. He won't probably ever see again."

Evidence markers sit next to a pair of shoes at the scene of a shooting on Macleod Trail South on Saturday. (Helen Pike/CBC)

That individual was taken to hospital in stable condition with shrapnel injuries, according to EMS.

Another person was taken to hospital with gunshot wounds, police said.

Rupchan said that person was believed to have been involved in the shooting, and police plan to interview him as soon as his condition stabilizes.

It's not yet known if there were any other injuries.

"It's still relatively early at this stage, so we're trying to determine if there are any other people injured," Rupchan said.

Police shut down four blocks on Macleod Trail South as officers investigated the nearby shooting. (Submitted)

The two vehicles involved in the incident appeared to be a grey Nissan Rogue and a black Ford Escape, police said.

Police said five or six individuals were involved in the shooting. Two offenders ran away on foot, police say.

Macleod Trail was shut down between 46th and 49th Avenue South as officers investigated. The road reopened at 4:45 p.m.

A multi-vehicle crash snarled an area just north of the road closure around 2:20 p.m., but police said it was unrelated to the shooting.

A driver had suffered a medical emergency and hit several other vehicles in the intersection of Macleod Trail and 42nd Avenue. There were no major injuries.