Police block a street after a mass shooting at a Fourth of July parade route in the Chicago suburb of Highland Park, Illinois, on July 5, 2022. Photo: Reuters/Cheney Orr

The man accused of attacking a Fourth of July parade in a Chicago suburb bought his rifle legally, fired more than 70 rounds from a roof, and dressed in women’s clothing to blend into the fleeing crowd afterwards, local officials said on Tuesday.

The suspect, 21-year-old Robert E. Crimo III, surrendered to police on Monday, hours after the attack in Highland Park, Illinois, in which six people were killed and more than 30 people were wounded.

Among the dead were Nicholas Toledo, a grandfather from Mexico in his 70s celebrating with his family among the flag-waving crowds at Monday’s parade, and Jacki Sundheim, a teacher at a nearby synagogue.

Officials told reporters the suspect had planned the attack for several weeks and fired into the crowd at random. Authorities were still considering what criminal charges to bring. It was not immediately clear if Crimo had a lawyer.

Crimo has distinctive facial tattoos, and wore women’s clothing on Monday in an apparent effort to mask his identity, Chris Covelli, a spokesperson for the Lake County Sheriff’s office, told reporters.

“He blended right in with everybody else as they were running around, almost as if he was an innocent spectator as well,” Covelli said. The suspect fled to his mother’s house nearby, and later borrowed his mother’s car.

Officials said they did not know the motive for the shooting in a predominantly Jewish neighborhood, but had no evidence of any antisemitic or racist basis. Investigators were reviewing videos he had made filled with violent imagery.

The suspect used a high-powered rifle for the attack, similar to an AR-15, which he dropped at the scene.

He had a similar rifle in his mother’s car, which he was driving when taken into custody by police, and owned other guns at his home, all of which were bought legally in Illinois, officials said.

Highland Park Mayor Nancy Rotering said the community of 30,000 was still in shock.

“This tragedy should have never arrived at our doorsteps,” she told NBC News. “As a small town, everybody knows somebody who was affected by this directly and, of course, we are all still reeling.”

President Joe Biden ordered US flags to be flown at half-staff in mourning until sunset on Saturday.

The US Supreme Court last month asserted a constitutional right to carry weapons in public in a ruling that made it easier for pro-gun groups to overturn modern gun regulations. It has since thrown out a lower court ruling upholding Maryland’s ban on assault weapons.

A string of mass shootings has renewed US debate about gun safety.

Congress last month passed its first major federal gun reform in three decades, providing federal funding to states that administer “red flag” laws intended to remove guns from people deemed dangerous.

The law does not ban sales of assault-style rifles or high-capacity magazines but does take some steps on background checks by allowing access to information on significant crimes committed by juveniles.