A "person of interest" has been arrested after a mass shooting at a July 4 parade in Highland Park, U.S. state of Illinois, which left six people dead, local police said on Monday. 

The arrest follows an hours-long manhunt. Police are still describing the 22-year-old man in custody, Robert E Crimo III, as a "person of interest" while they investigate and connect him to the scene.

Among the deaths, five people died at the scene and one individual died at the hospital after suffering severe injuries, according to the police.

A total of 26 patients were received at Highland Park Hospital, reported CNN. The patients ranged in age from 8 years old to 85 years old, according to Brigham Temple, medical director of NorthShore University Health System.

Highland Park is located about 25 miles north of downtown Chicago. The shooting began at 10:14 a.m., when the parade was approximately three-quarters of the way through.

Witnesses said parade attendees initially thought gunshots were fireworks, reported CNN. They realized a shooting happened after seeing a man with a wound on his head, the reports said. 

U.S. President Joe Biden responded on Monday to the mass shooting, saying he and first lady Jill Biden are "shocked by the senseless gun violence that has yet again brought grief to an American community on this Independence Day." 

He said he's surged federal law enforcement to "assist in the urgent search of the shooter."

In a speech, Illinois Governor J.B. Pritzker said "there are no words" to describe the loss and grief the families of those killed and injured feel this holiday.

"It is devastating that a celebration of America was ripped apart by our uniquely American plague," Pritzker said.

It is the latest mass shooting to hit the U.S. Halfway through the year, there have been at least 311 mass shootings, including at least three others on July 4, though without any fatalities, according to the Gun Violence Archive. 

On June 25, 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 gun safety law requires young people aged 18 to 21 to undergo enhanced background checks, but the law alone is unlikely to tackle the gun violence issue.

Moreover, the U.S. Supreme Court added to the tension over gun control in late June by striking down a century-old New York State law requiring gun owners to have probable cause to carry a concealed weapon.

'Heightened threat environment'

According to ABC News, in the weeks before the mass shooting in Highland Park, federal law enforcement officials had again been on alert because of a "heightened threat environment" fueled in part, they said, by domestic extremists and social upheaval.

U.S. Homeland Security Secretary Alejandro Mayorkas detailed his concerns last month, and his department released an assessment of some of the threats the U.S. was facing.

"As recent acts of violence in communities across the country have so tragically demonstrated, the nation remains in a heightened threat environment, and we expect that environment will become more dynamic in the coming months," Mayorkas said.

The tragedy in Highland Park is the 15th mass killing of 2022 and the 11th mass shooting of the holiday weekend, according to the Gun Violence Archive, a nonprofit organization that tracks gun-related violence in the country. It is also one of two mass shootings in the Chicago region alone on Monday.

Around midnight on Monday, five people were injured in a shooting on Chicago's South Side.

The U.S. has recorded 311 cases of mass shootings so far this year, and as more than 22,000 people died from gun violence, without easing from the jump in the previous two years, according to Gun Violence Archive.

The Gun Violence Archive defines a mass shooting as one in which at least four people are shot, excluding the shooter.

Last year was the worst year on record since the Gun Violence Archive began tracking mass shootings in 2014. There were a total of 692 mass shootings in the U.S. in 2021, the nonprofit says.

(With input from agencies)

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