Highland Park shooting: police say suspect used women’s clothing disguise; 7 now dead

Police seeking clues for a possible motivation combed through the social media profile and published songs of the alleged attacker in the shooting that left at least seven dead and 30 wounded in a Chicago suburb on the Fourth of July.

Robert Crimo, 21, was detained hours after the shooting Monday as a person of interest in the case, said the police chief of Highland Park, Illinois. Investigators have stopped short of calling Crimo a suspect, but on Tuesday they described finding evidence that he disguised himself in “women’s clothing” to avoid being captured after he fired a high-powered rifle styled in the fashion of an AR-15 at strangers more than 70 times.

Crimo had legally bought that rifle, along with at least one more, as well as some pistols, before carrying out an attack that had evidently been planned for weeks, said Chris Covelli, the leader of a police taskforce investigating major crimes in the Illinois county that includes Highland Park.

Crimo had posted dozens of videos with ominous songs showing images of himself or cartoon figures holding rifles with threatening messages, piquing authorities’ interest by Tuesday.

Related: Chicago mass shooting: man in custody after six shot dead at Fourth of July parade

YouTube has taken down Crimo’s page, where he was known as Awake the Rapper. Instagram and Twitter have also terminated Crimo’s accounts.

One video shows Crimo sitting in a classroom and then reaching inside his backpack before the screen goes black. The next frame shows Crimo in the same classroom with scattered papers and other objects on the floor as disturbing music plays in the background.

In another video, a stick figure appears to have been shot by police.

The videos contained disturbing lyrics, with Crimo reciting messages such as: “Everything has led up to this. Nothing can stop me, even myself.” His social media pages displayed the logo of a Finnish white supremacist organization called Suomen Sisu.

Covelli said investigators had not been tipped off to the videos before the shooting.

Police officers equipped with rifles and body armor arrested Crimo after they pulled his car over after he blended in with the panicked parade crowd and fled about five miles north of the mass shooting scene on Monday. Authorities hours earlier had released his photo and an image of his silver Honda Fit.

Covelli said local officers recognized Crimo in surveillance footage that they reviewed after the shooting, which allowed them to identify him and detain him in a relatively short time.

Authorities had still not said what charges Crimo faces following his detention as of early Tuesday afternoon.

At least six people who were killed were adults, Covelli said. By Tuesday afternoon, a seventh victim who had been taken to hospital following the shooting had died, though additional details about that person weren’t immediately available, Covelli confirmed to the Guardian.

Covelli said that, as of Tuesday afternoon, investigators had not found evidence that the victims were targeted because of their race, religion or some other federally protected status, which would dictate whether or not authorities treated the mass shooting as a possible hate crime.

The shooter opened fire about 10.15am, when the parade was about three-quarters through, according to authorities. He had used a ladder attached to a building in that vicinity to climb atop a business and fire sniper-style from there, Covelli said.

Police have said they recovered the rifle at the scene.

“It is devastating that a celebration of America was ripped apart by our uniquely American plague,” the Illinois governor, JB Pritzker, said at a news briefing.

The shooting comes barely a week after Joe Biden signed into law a bipartisan gun bill intended to prevent dangerous people from accessing firearms. The fact that Crimo legally purchased the alleged murder weapon has reignited the nationwide debate about whether the US can do more to rein in access to high-capacity guns.

Highland Park’s municipal government banned assault-style guns within city limits in 2013. But Monday’s killings illustrated the limited effect of such a measure without support at the state and federal level.

Biden on Tuesday ordered all flags on federal property across the US to be flown at half-staff to honor those slain in Highland Park the previous day.

The Illinois suburb is a tight-knit bedroom community of about 30,000 people, once home to the Chicago Bulls superstar Michael Jordan.

It is also where 1980s John Hughes classics such as Ferris Bueller’s Day Off, Sixteen Candles and Weird Science were filmed for the big screen.

• This article was amended on 5 July 2022 to give the shooting suspect’s age as 21, not 22 as police had originally stated.