Police have identified the suspected shooter as 45-year-old Gary Martin, an employee of the firm whom they said was killed after exchanging gunfire with officers inside the 29,000-square-foot plant.
Aurora Police Chief Kristen Ziman said Friday evening that authorities were currently "unsure of the motive of this act of violence."
The Chicago Sun Times reported that the mother of the alleged gunman said her son had been laid off two weeks ago and was "stressed out" before the shooting.
Local officials gathered to mourn the victims, saying the community will work to recover from the shooting.
"We will heal. We will come together as one community and stand by those in pain from today’s great loss. We will stand together with those officers shot in the line of duty. We will come together and heal as one Aurora," Mayor Richard Irvin said.
Pritzker, who entered office last month, spoke during a press conference Friday evening about how the shooting was part of a larger trend.
"Tomorrow the families of the victims will be less than whole. They join a group that should not exist and yet continues to grow," he said.
President TrumpDonald TrumpSix big off-year elections you might be missing Twitter suspends GOP Rep. Banks for misgendering trans health official Meghan McCain to Trump: 'Thanks for the publicity' MORE took to Twitter on Friday evening to praise the law enforcement response and offer condolences for victims.
White House press secretary Sarah Huckabee Sanders said earlier that Trump "has been briefed and is monitoring the ongoing situation" in Aurora.
Great job by law enforcement in Aurora, Illinois. Heartfelt condolences to all of the victims and their families. America is with you!— Donald J. Trump (@realDonaldTrump) February 15, 2019
Police had warned about an active shooter situation earlier in the day and urged people to avoid the area.
"Shooter is no longer a threat to the area," Aurora police confirmed in a tweet after city officials said shortly after 3 p.m. that "the shooter has been apprehended."
EMERGENCY UPDATE | 3 p.m.— City of Aurora, IL (@CityofAuroraIL) February 15, 2019
THE SHOOTER HAS BEEN APPREHENDED! The area is still on lock down!
More information will be provided soon.
Active Shooter Incident has been secured. Shooter is no longer a threat to the area. Continued police presence will remain as investigation continues. Parents please contact your local school districts for dismissal plan https://t.co/P4y7X7K4og— Aurora (IL) Police (@AuroraPoliceIL) February 15, 2019
A man who said he was an employee at the manufacturing company told a local ABC affiliate that he recognized the shooter as a coworker.
"One of the guys was up in the office, he said this person was shootin', and, he come running down and he was bleeding pretty bad, and the next thing you know he was walking back and forth, I heard more shots, and we just left the building," the employee said.
The Herald reported that SWAT teams were called to the scene, along with the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF).
Aurora is about 38 miles west of Chicago.
Sen. Dick DurbinDick DurbinManchin: Negotiators to miss Friday target for deal on reconciliation bill Democrats look for plan B on filibuster The Memo: Cuts to big bill vex Democrats MORE (D-Ill.) tweeted his sympathies.
"My heart breaks for Aurora," he wrote. "I'm tracking updates on the situation with my staff. Thank you to the members of law enforcement who are responding to the emergency."
Updated: 7:22 p.m. ET