HIGHLAND PARK, ILL. -- The mayor of a Chicago suburb says a seventh victim has died after shots rang out Monday during a Fourth of July parade, where more than 30 people were also injured.

Nancy Rotering told CNN that the death toll has risen in the attack in Highland Park, Ill., the latest community to be scarred by a mass shooting in America.

Police earlier told a news conference that the suspect planned the attack for several weeks and wore women's clothing to disguise his identity.

Deputy Chief Christopher Covelli of the Lake County Sheriff's Office said Robert E. Crimo III wore the clothing to conceal his facial tattoos and to blend into the crowd as he fled the scene.

Covelli said Crimo brought a legally purchased high-power rifle to the parade, accessed a roof of a business via a fire escape ladder and fired more than 70 rounds at people gathered at the Independence Day celebration.

After the attack, police said he dropped his rifle and escaped, blending into the crowd as if he were an "innocent spectator" and walking to his mother's house, where he borrowed her car.

Police put out an alert with information about Crimo and the vehicle, and a member of the public who spotted the vehicle dialed 911 and officers were able to apprehend him.

Covelli said a second rifle was located in the vehicle, also purchased by Crimo, and the suspect remains in custody. An update on charges is expected later today.

The deputy chief added there is no indication that anyone else was involved in the attack and a motive has not been determined. Police have no information that it was religiously or racially motivated, Covelli said, adding it appears to be "completely random."

Covelli added Crimo is actually 21, not 22 as previously reported, and is a resident of Highwood, Ill.

Rotering said at the news conference that Tuesday is a day of grieving together, to pause and to remember those who died as well as honour those who were injured.

She also told CNN that she was once the alleged gunman's Cub Scout pack leader.

"Many years ago, he was just a little boy, a quiet little boy that I knew," Rotering said. "It breaks my heart. It absolutely breaks my heart."

Video clips posted to social media showed the festivities collapsing into panic as revellers realized they were under fire and scrambled for cover.

The violence erupted just six weeks after a deadly elementary school rampage in Uvalde, Texas, killed 19 children and two teachers.

The confluence of America's birthday and a worsening epidemic of gun violence is sure to conjure a familiar brew of hurt, helplessness and outrage.

A statement from Homeland Security Secretary Alejandro Mayorkas described a "celebration of our nation punctured by tragedy," and commended the efforts of local law enforcement.

"The security of our homeland requires more; It requires all of us, together, to address the epidemic of targeted gun violence" with new community-based prevention and intervention strategies.

In a tweet late Monday, Prime Minister Justin Trudeau offered condolences to the victims, their families and the Highland Park community.

They "wanted nothing more than to celebrate their country … but instead had their lives change forever," Trudeau tweeted.

"To the injured, and to the loved ones of the victims: Canadians are keeping you in our thoughts."

This report by The Canadian Press was first published July 5, 2022.

   -- With files from The Associated Press