Hours after the attack, police said a suspect, 22-year-old Robert E. Crimo III, surrendered to authorities.
Police said the gunman climbed to the roof of a business using a ladder in an alley. The attack turned a civic display of patriotism into a scene of mayhem.
Amairani Garcia is a Highland Park resident.
"I was just scared. I was scared for my daughter who is just six years old. I didn't know what was going on. You know we just heard gun shots and people running and screaming all over the place. And chairs, I remember chairs and everything was on the floor. I remember grabbing her and running with her and telling her come on baby we've got to run we've got to run, we have to get somewhere safe."
The main street in Highland Park became a crime scene spanning blocks, strewn with abandoned chairs and flags.
The wounded ranged in age from 8 to 85, including five children.
Nicolas Toledo, a man his 70s, was the first victim identified as of late Monday by his family.
Another victim was Jacki Sundheim, a teacher at a synagogue in Highland Park. The North Shore Congregation Israel confirmed her death in an email to congregants.
Police said they did yet know the motive for the shooting.
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.
The accounts showed a man with physical characteristics and facial tattoos similar to those in photos of the suspect released by police.
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.
"This murderer will be brought to justice."
The Democratic governor of Illinois, J.B. Pritzker, linked the July 4th attack to spate of gun massacres, from Buffalo, New York, to Uvalde, Texas, that reignited debate over firearms in the U.S.
"I am furious because it does not have to be this way, and yet we as a nation, well, we continue allow this to happen. While we celebrate the Fourth of July just once a year, mass shootings have become our weekly, yes weekly American tradition."
President Joe Biden said he and his wife Jill were "shocked by the senseless gun violence that has yet again brought grief to an American community on this Independence Day."
