The gunman climbed to the roof of a business using a ladder in an alley, police said. The attack turned a civic display of patriotism into a scene of panicked mayhem.
Hours later, police announced that they had a suspect in custody after 22-year-old Robert E. Crimo III surrendered to authorities.
“It sounded like fireworks going off,” said retired doctor Richard Kaufman who was standing across the street from where the gunman opened fire, adding that he heard about 200 shots.
“It was pandemonium,” he said. “People were covered in blood tripping over each other.”
The shooting comes with gun violence fresh on the minds of many Americans.
A gunman on May 24 murdered 19 school children and two teachers at an elementary school in Uvalde, Texas, just 10 days after a man shot dead 10 people at a grocery store in Buffalo, New York.
Police said they did not know what the motive was for the shooting in Highland Park on Monday. Those wounded ranged in age from 8 to 85, including four or five children.
The New York Times named one of the dead as 76-year-old Nicolas Toledo, who was in a wheelchair and had not wanted to attend the parade, but his disabilities required that he be around someone full time and his family had not wanted to miss the event.
“We were all in shock,” his granddaughter Xochil Toledo said. “We thought it was part of the parade.”
At least one of those killed was a Mexican national, a senior Mexican foreign ministry official said on Twitter. (Reuters)