The suspect, 21-year-old Robert E. Crimo III, surrendered to police on Monday, hours after the attack in Highland Park, Illinois, that left seven people dead more than 30 others wounded.

Police revised the confirmed casualty toll on Tuesday with the death of a seventh person who had been hospitalised after the attack.

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 spokesman 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 neighbourhood with a large Jewish population, but had no evidence of any anti-Semitic 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.

Rotering, the city’s mayor, said she knew the suspect when he was a little boy and a Cub Scout and she was a Cub Scout leader.

“What happened? How did somebody become this angry, this hateful?,” she said.

Social media and other online posts written by accounts that appeared to be associated with either Crimo or his rapper alias, Awake The Rapper, often depicted violent images or messages.

One music video posted to YouTube under Awake The Rapper, for example, showed drawings of a stick figure holding a rifle in front of another figure spread on the ground.

Officials had earlier said the suspect was 22, but corrected that to 21 at Tuesday’s briefing.

Rotering said on Tuesday that she did not know where the gun the gunman used came from but added that it was legally obtained.

“Our nation needs to have a conversation about these weekly events involving the murder of dozens of people with legally obtained guns,” she said.

The suspect’s father, Bob Crimo, ran Bob’s Pantry and Deli in Highland Park for at least 18 years, according to a Chicago Tribune business profile.

Bob Crimo closed the deli in 2019 before he unsuccessfully ran against Rotering for mayor of Highland Park.