Over the Fourth of July weekend, many gathered to enjoy festivities and celebrate. However, the joyous time turned to tragedy when a gunman opened fire on residents of Highland Park, Illinois, on Monday, CNN reports.

The deadly massacre left at least six people dead and dozens seriously injured. Authorities took the suspected shooter, Robert E. Crimo III, into custody after a North Chicago officer ordered a traffic stop while Crimo was in his vehicle.

He did not comply and engaged officers in a brief chase before he was taken into custody. According to CNN, he was transferred to the police department in Highland Park Monday evening. 

Highland Park Mayor Nancy Rotering noted on the Today show that Crimo’s online postings “reflected a plan and a desire to commit carnage for a long time in advance,” Newsweek reports.

“And it’s one of those things where you step back and you say, ‘What happened? How did somebody become this angry, this hateful?’ To then take it out on innocent people who literally were just having a family day out,” Rotering continued, NBC News reports.

Rotering said the gun violence discussion should center on “the fact that there are weapons of war on our streets, that people can legally obtain these and then take out dozens of people,” CNN reports.

The 21-year-old used a “high-powered rifle,” and police said his attack was “random” and “intentional,” CNN reports. Crimo positioned himself on a business rooftop and opened fire on the parade about 20 minutes after it began.

As shots rang out, people left sporting chairs, baby strollers and American flags behind. 

“It sounded like fireworks going off,” said retired doctor Richard Kaufman, who stood across the street from where the gunman started shooting, according to Reuters.

Eyewitnesses said they grabbed their children and family members while running to safety. Some took refuge behind dumpsters and in nearby stores. One parade-goer recalled seeing a girl shot and killed and a man shot in the ear with blood flowing down his face. 

“It looked like a battle zone, and it’s disgusting. It’s really disgusting,” Zoe Pawelczak, who attended the Independence Day parade with her father, said, according to CBS 58.

Stacy Shaulman, a Highland Park resident, waited with others outside the police station to witness Crimo’s arrival, according to the Chicago Sun-Times.

“It’s been a horrific day,” Shaulman said. “I’m glad they got him. And, unfortunately, he’s a Highland Park kid, and people knew his family. His family has been around a long time.”

As of 9 p.m., police had not filed charges and gave no reason for the motive for the shootings.

Authorities of the Federal Bureau of Alcohol, Tobacco, Firearms and Explosives are examining the history and ownership of Crimo’s rifle.

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