Updated

At least six people were killed and more than 30 others were hospitalized following a shooting at a 4th of July parade in Highland Park, Illinois, on Monday and police have arrested a suspect in the shooting. 

Police said Crimo was considered armed and dangerous and was pulled over by police Monday after a brief pursuit, following an hours-long manhunt. 

The city of Highland Park initially stated that 16 people were injured and five were killed, but officials amended the total to six dead and 31 injured during an afternoon press conference. Authorities said a "high-powered" rifle had been located on a rooftop, but did not offer more details. 

Authorities earlier identified 22-year-old Robert "Bobby" E. Crimo III as the suspect. They said he was driving a 2010 Silver Honda Fit with the license plate DM80653 and is from the area. 

Highland Park July 4 shooting

Robert E. Crimo, 22, has been identified as a person of interest in the July 4th parade attack in Highland Park, Illinois in which at least six people were killed.  (Highland Park Police Department)

Chris Covelli, spokesman for the Lake County Crimes Task Force said earlier at least 100 law enforcement officers were on scene "aggressively" looking for the suspect. He appealed to nearby businesses and parade attendees to review their photos and videos to give to police for the investigation.  

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Covelli said several of the victims – all adults – died at the scene and at least one died after being transported to a hospital. The other injured victims were transported to Lake and Cook County Hospitals and their conditions ranged from "serious" to "critical." At least one of those critically injured was a child, authorities said. 

Residents within about a mile radius were told to shelter in place as authorities investigated.  

The shooting occurred at a spot on the parade route where many residents had staked out prime viewing points early in the day for the annual celebration. Dozens of fired bullets sent hundreds of parade-goers running for their lives. 

Authorities set up a reunification post at the Highland Park Police Department for families who had been separated. 

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Highland Park Mayor Nancy Rotering urged residents to avoid the downtown area as police respond to the incident. 

"Highland Park Police are responding to an incident in downtown Highland Park," she announced on Twitter. "Fourth Fest has been canceled. Please avoid downtown Highland Park. More information will be shared as it becomes available."

Democratic Illinois Gov. Pritzker also confirmed that he and his staff are "closely monitoring" the situation.

"It is devastating that a celebration of America was ripped apart by our uniquely American plague," Illinois Gov. J.B. Pritzker said at a news conference later Monday. 

"I'm furious because it does not have to be this way... while we celebrate the Fourth of July just once a year, mass shootings have become a weekly — yes, weekly — American tradition."

Pritzker, a Democrat, promised support for the community as well as to bring gunman to justice.

"There are no words for the kind of evil that shows up at a public celebration of freedom, hides on a roof and shoots innocent people with an assault rifle," Pritzker said.

"Our hearts go out to the people of Highland Park and all those affected by today's tragic events," Chicago Police Superintendent David O. Brown said in a tweet. "The #ChicagoPolice Department stands with the City of Highland Park during this devastating time." 

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Lake County Coroner Jennifer Banek said the five people killed at the parade were adults and she doesn't have information on the sixth victim who was taken to a hospital and died there.

Dr. Brigham Temple, medical director of emergency preparedness for NorthShore University Health Center, said the Highland Park hospital received 26 patients after the attack and all but one had gunshot wounds. Their ages ranged from 8 to 85, and Temple estimated that four or five patients were children.

He said 19 of them were treated and discharged. Others were transferred to other hospitals, while two patients, in stable condition, remained at the Highland Park hospital.

The shooter opened fire around 10:15 a.m., when the parade was about three-quarters through, authorities said.

Several nearby cities canceled events including parades and fireworks, some of them noting that the Highland Park shooter was still at large. Evanston, Deerfield, Skokie, Waukegan and Glencoe canceled events.

More than a dozen police officers on Monday evening surrounded a home listed as an address for Crimo in Highland Park. Some officers held rifles as they fixed their eyes on the home. A large armored truck, marked "Police Rescue Vehicle," occupied the middle of the road near the residence. Police blockaded roads leading to the home in a tree-lined neighborhood near a golf course, allowing only select law enforcement cars through a tight outer perimeter.

The Department of Homeland Security confirmed that Secretary Alejandro Mayorkas has been briefed on the shooting and that DHS is coordinating with local, state, and federal partners to offer the Department's support. 

Rep. Brad Schnider, D-Ill, says he was in attendance at the parade at the time of the shooting. He confirmed he is safe in a tweet, but did not offer any details regarding the situation.

"Today a shooter struck in Highland Park during the Independence Day parade. My campaign team and I were gathering at the start of the parade when the shooting started," Schnider wrote. "My team and I are safe and secure. We are monitoring the situation closely and in touch with the Mayor."

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"Hearing of loss of life and others injured. My condolences to the family and loved ones; my prayers for the injured and for my community; and my commitment to do everything I can to make our children, our towns, our nation safer. Enough is enough!" he added. 

The Associated Press contributed to this report.