HIGHLAND PARK, Ill — At least six people were killed  and at least 24 injured in a mass shooting at a 4th of July parade in the wealthy Chicago suburb on Monday morning, police said.

Authorities said the gunman, who was still at large hours later, randomly opened fire with a “high-powered rifle” from the roof of a building overlooking the parade route shortly after 10 a.m Monday morning.

Five adults died at the scene and another succumbed to their injuries after being rushed to hospital, police said.

The shooter, who police warned is still “armed and dangerous”, was described as a white male with long dark hair and is aged 18 to 20 years. He was wearing a blue or white t-shirt, police said.

“I heard 20 to 25 shots, which were in rapid succession. So it couldn’t have been just a handgun or a shotgun,” local resident Miles Zaremski told reporters.

“This morning at 10.14, our community was terrorized by an act of violence that has shaken us to our core,” Mayor Nancy Rotering said at the news conference.

“Our hearts go out to the families of the victims at this devastating time,” Mayor Rotering said. “On a day that we came together to celebrate community and freedom, we are instead mourning the tragic loss of life and struggling with the terror that was brought upon us.”

Footage from the scene showed hundreds of parade-goers — some visibly bloodied — fleeing the parade route as the gunshots rang out just 10 minutes after the parade began.

Chairs, baby strollers, children’s bikes, blankets and US flags were among the items left behind as people fled.