Deputy Chief Christopher Covelli of the Lake County Sheriff’s Office said the rifle used in the shooting appeared to have been purchased legally by Mr. Crimo in the Chicago area, and that Mr. Crimo had legally purchased other guns, including the second rifle. Other firearms were found in the place where he was living.
The Bureau of Alcohol, Tobacco, Firearms and Explosives was running tests on the recovered weapon and ammunition.
The motive for the shooting is unknown.
Chief Covelli said Mr. Crimo planned the shooting for several weeks, but that the authorities had not yet established what his motive was. “We have no information to suggest at this point it was racially motivated, motivated by religion, or any other protected status,” the chief said, adding that there was no indication that anyone else was involved.
The suspect used a disguise.
The authorities said the gunman wore women’s clothing to disguise his identity. He climbed up a fire escape ladder to gain access to the roof where he staged his attack, and then after the shooting, he climbed back down and left the scene on foot, blending in with fleeing paradegoers. The police said he walked to his mother’s home in Highland Park and borrowed her car. He was arrested when the police in a neighboring town spotted the car and pulled him over for a traffic stop.
It was one of several multiple shootings in recent days.
The mass shooting in Highland Park was the fourth in Illinois since Friday in which at least four people were struck, according to the Gun Violence Archive. The state has among the strictest gun-safety laws in the nation — including universal background checks, red flag warnings and safe storage requirements — but it is surrounded by states like Indiana that have far fewer restrictions to gun purchase and ownership.
Ten hours before the parade shooting, at about midnight, five people were shot at a housing complex in the Greater Grand Crossing neighborhood on Chicago’s South Side. On Friday, two people were killed and seven injured in two separate shootings in Chicago, according to the Gun Violence Archive.
Also on Monday, the group reported, there were shootings with four or more people injured in Boston, Sacramento, Kansas City, Mo., and Richmond, Va.