Highland Park (United States) (AFP) - A gunman armed with a high-powered rifle shot dead at least six people at a parade to mark US Independence Day in a wealthy Chicago suburb on Monday -- the latest in a series of shocking mass shootings, this time on a holiday celebrating all things American.

Emergency officials in Highland Park, Illinois said around two dozen people, including children, were wounded with some in critical condition, and a massive police manhunt was underway for the shooter, who was still on the loose.

Police said they had apprehended a 22-year-old suspect named Robert E Crimo III, warning that he was considered armed and "very dangerous." A Chicago musician of the same age and with the same name goes by the stage name "Awake the Rapper" online.

Firing into the holiday crowd from a nearby rooftop, the gunman triggered scenes of chaos as panicked onlookers ran for their lives, leaving behind a parade route strewn with chairs, abandoned balloons and personal belongings.

"Everyone thought it was fireworks," one parade-goer, identified only as Zoe, told CNN.

"My dad thought it was part of the show, and I'm like, 'Dad, no... something is wrong.' And I grabbed him. And I looked back at him, and then it was just a sea of panic, and people just falling and falling."

As they ran, she said that some 20 feet behind her, "I saw a girl shot and killed... saw her die."

Zoe said they first hid behind a dumpster before police pulled them into the basement of a sporting goods store with other parade spectators, several of whom were injured, including a man who appeared to have been shot in the ear and a girl who was shot in the leg.

When they were finally able to leave, she told CNN, the parade route resembled "a battle zone. And it's disgusting."

Police officials said the shooting began at 10:14 am, when the parade was approximately three-quarters of the way through.

"It sounds like spectators were targeted... So, very random, very intentional and very sad," said Lake County Major Crime Task Force spokesman Christopher Covelli.

Lake County coroner Jennifer Banek said five of the six people killed, all adults, had died at the scene. The sixth was taken to hospital but succumbed to wounds there.

Fire chief Joe Schrage said among the wounded was at least one child, in critical condition.

Dr Brigham Temple of Highland Park Hospital, where most of the victims were taken, said that it was treating 25 people with gunshot wounds aged eight to 85.

He said "four or five" children were among them, and that 16 people were later discharged.

Police said the shooter was using a "high-powered rifle," and "firearm evidence" had been located on the rooftop of a nearby business.

"All indications is he was discreet, he was very difficult to see," said Covelli.

From Celebration To Mourning

The shooting cast a pall over America's most patriotic holiday, in which towns and cities across the country hold parades such as the one in Highland Park while citizens -- many dressed in variations on the US flag -- hold barbecues and other celebrations.

"On a day that we came together to celebrate community and freedom, we're instead mourning the tragic loss of life and struggling with the terror that was brought upon us," Highland Park's mayor Nancy Rotering said.

President Joe Biden voiced his shock and vowed to keep fighting "the epidemic of gun violence" sweeping the country.

"I'm not going to give up," he said.

Last week, Biden signed the first significant federal bill on gun safety in decades, just days after the Supreme Court ruled that Americans have a fundamental right to carry a handgun in public.

The shooting is part of a particularly grim wave in the gun violence crisis in the United States, where approximately 40,000 deaths a year are caused by firearms, according to the Gun Violence Archive website.

The deeply divisive debate over gun control was reignited by two massacres in May that saw 10 Black supermarket shoppers gunned down in upstate New York and 21 people, mostly young children, slain at an elementary school in Texas.

According to the Gun Violence Archive, there have been 309 mass shootings carried out in the US so far in 2022 -- including at least three others on July 4, though without any fatalities.