Another person involved in the gunfire may still be at large, Oak Brook Police Chief James Kruger said Thursday during a news conference. A man in his 30s who police think "is one of the offenders from this incident" was also shot, he said.

"It is our understanding that the two suspects involved in the shooting were known to each other and shot at each other, and the other victims were injured by ricochet gunfire that the two suspects had fired at each other," Kruger said during a news conference.

"It was crazy," Oakbrook Center shopper Camila Reyes told CNN affiliate WLS. "It was a lot of shooting. It was a lot of shooting. It was so loud."

"Everyone was panicking," another witness, Diane Sprague, told the news outlet.

The injured were taken to hospitals and include two women in their 40s, a woman in her 20s and the suspect, police said. Another person hurt an ankle trying to flee the scene.

A vehicle connected to a suspect was impounded, and the motive is still under investigation, Kruger said.

The shooting sent the mall into lockdown amid busy holiday shopping.

"We tried to keep everyone calm and safe -- stay away from the windows. We locked the doors, stayed away from the back door," Sprague told WLS. "There were children, elderly people -- made sure everybody was not injured."

About 100 police officers from area agencies, including the entire staff of the Oak Brook Police Department, cleared the mall, Kruger said. They worked store-by-store after shoppers and employees were asked to shelter in place as SWAT and tactical teams searched the site.

The mall was expected to reopen Friday morning.