A man is in police custody after an hours-long manhunt near the Chicago suburb of Highland Park where a deadly shooting took place during an Independence Day parade.

Police arrested a 22-year old man suspected in a deadly shooting at a July 4th parade in Highland Park, a suburb of the US city of Chicago, police said.

The man was "taken into custody without incident" after he was spotted driving on a highway near Chicago, police told the Chicago Sun-Times.

At least six people were killed and 30 wounded in the shooting, authorities said on Monday.

The Highland Park chief of police told a press conference early Monday evening that authorities had identified a white male who comes from the area as a "person of interest" in the shooting. Police also released a description of the suspect's car and license plate.

Lake County Major Crime Task Force spokesman Christopher Covelli earlier said authorities believed there was only one shooter and warned that he should still be considered armed and dangerous.

"Our community was terrorized by an act of violence that has shaken us to our core. Our hearts go out to the families of the victims during this devastating time," Highland Park Mayor Nancy Rotering said.

US President Joe Biden on Monday said he and first lady Jill Biden were "shocked by the senseless gun violence that has yet again brought grief to an American community on this Independence Day.''

How did the shooting happen?

Shots were fired along the route only minutes after the parade to celebrate Independence Day began.

The gunman opened fire on parade-goers from a concealed position on a rooftop using a "high-powered rifle'' that was recovered at the scene, according to task force spokesman Covelli.

"It sounds like spectators were targeted...So, very random, very intentional and very sad," he added.

Staff at NorthShore Highland Park Hospital treated 26 people, and five were transported to NorthShore Evanston Hospital, spokesperson Jim Anthony said.

"The vast majority suffered gunshot wounds. Remaining individuals sustained injuries as a result of chaos at the parade," Anthony added.

Gina Troiani and her son were ready to walk onto the parade route when she heard people yell about a shooter.

"We just start running in the opposite direction,'' she said. "There were people that got separated from their families, looking for them. Others just dropped their wagons, grabbed their kids and started running.''

Debbie Glickman, a Highland Park resident, was on a parade float with coworkers when she saw people running from the area.

People, some visibly bloodied, fled the scene upon hearing several loud bangs, CBS 2 television of Chicago reported, citing a producer who was at the parade.

"My condolences to the family and loved ones; my prayers for the injured and for my community," US Representative Brad Schneider, whose district includes Highland Park, said on Twitter. "Enough is enough!"

Gun violence in the United States

The shooting comes with gun violence fresh on the minds of many Americans.

Last month US President Joe Biden signed the first major federal gun reform law in three decades.

US Lawmakers reached the bipartisan agreement on gun control only weeks after a gunman in Buffalo, New York, opened fire on shoppers killing 10 people in what has been called a racist shooting.

Less than two weeks later, a shooter killed 19 children and two teachers at an elementary school in Uvalde, Texas.

Gun-related killings in the US are higher than in most other high-income countries. In 2019, for example, 4.12 people per 100,000 were killed by guns, while only 0.5 were killed in Canada.