At about 6:30 p.m., a North Chicago police officer spotted 22-year-old Robert "Bobby" E. Crimo III at Route 41 and Buckley Road, police said.
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There was a brief pursuit, but the vehicle was stopped at Westleigh Road and Route 41 in Lake Forest.
WATCH: Person of interest in parade shooting placed into custody after chase
Video: Person of interest in parade shooting placed into custody after chase
Crimo was taken into custody without incident. He was then transported to the Highland Park Police Department, sources told ABC7.
"It was just all really surreal. I really didn't know what I was seeing but yeah it was just like a dream almost. It was crazy," said Ryan Lerman, who witnessed the arrest.
The shooting, which happened at a 4th of July parade, left six people dead and at least 31 injured.
WATCH: Person of interest in parade shooting in custody, police say
Police announce capture of person of interest in Highland Park parade shooting
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Crimo is from the area. Some witnesses to the carnage told ABC7 Crimo lived in Highland Park. He has ties to Rockford, De Kalb and Elgin.
"I've definitely heard his name before. I know that he's a Highland Park resident, and went to Highland Park High School," said Lauren Sachs, who witnessed the shooting.
The father of the person of interest had previously run for Mayor of Highland Park in 2019, according to three individuals who knew him and public news reporting from the time.
The father, Robert Crimo Jr., was defeated by incumbent Mayor Nancy Rotering, according to ABC7 election results, and only received 28% of the vote.
A local business owner in Highland Park who grew up with Crimo Jr., the father, told ABC News that he was "trying his hardest to help his community" but "probably didn't have that much of a chance."
Law enforcement sources confirmed to ABC News that Crimo's social media posts are part of the ongoing investigation. One video shows cartoon characters being shot, according to ABC News.
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The gunman appeared to be firing from a roof, Chris Covelli with the Lake County Major Crimes Task Force said.
Highland Park parade shooting victims range in age from 8 to 85 years old, doctors say
A firearm was recovered from the scene.
Covelli said hundreds of officers including with Illinois State Police and the FBI were searching for the shooter.
Individuals who have information to share with police are urged to contact 1-800-CALL-FBI.
ABC News contributed to this report.