Highland Park Police Chief Lou Jogmen was with his family at the Highland Park Fourth of July parade when gunfire erupted.
Within minutes, dozens of people were wounded, resulting in the death of seven people.
"At about 10:15, you heard the indistinguishable sound of gunfire, I mean no question. No question whatsoever,” he told CNN. “The challenge was it went from a nice, beautiful day to complete chaos."
His agency joined a long list of police departments forced to respond to a mass shooting. Jogmen told CNN that the gunman’s positioning on a rooftop made it challenging for officers to fire back.
“The noise was bouncing off the buildings. People were pointing in different directions," he said.
Investigators said the alleged gunman dressed in women’s clothes to disguise himself. After the gunman fired 70 rounds into the crowd, he got away.
The incident left Jogmen seeking answers.
"That's the first thing people want to know; that's what we want to know, why, why,” he said. “At this point, I don't think I can give you a why based on what I’m hearing from my investigators. We'd love to have that reason out there. So people could process, but not sure that we're there yet."