John Probst says he recognized the gunman.
An employee at the Henry Pratt company, which specializes in making valves, Probst told CNN affiliate WLS-TV on Friday that he saw a man holding what appeared to be a pistol with a laser scope. He recognized him 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," Probst said.
Probst told WLS there were about 30 people in the building at the time of the shooting. Probst said he and a coworker escaped through the back door. Probst said a nearby resident allowed him and his coworker to shelter in a home.
Five people were killed in the shooting in Aurora, Illinois, about 45 miles from Chicago. The suspected shooter, identified as 45-year-old Gary Martin, was also killed. Martin was an employee at the company where the shooting occurred, police said.
Five officers were wounded during the shooting and a sixth is dealing with a knee injury, according to Aurora Police Chief Kristen Ziman. State and federal agencies swarmed the industrial area.
At nearby business, 'We have our doors locked'
One block away, Fanny Cano, a secretary at pallet company Diaz Pallets, told CNN that about eight employees were on lockdown.
"It's scary," she said. "A police officer came and told us not to go out because it's dangerous. And a person who was coming to drop off some pallets called us to say to stay inside, there's shooting outside."
Cano said employees at the company use a lot of nail guns, so they didn't hear any gunfire. She did receive a call from West Aurora High School, where her daughter attends, which was also on lockdown. Cano said being stuck inside was terrifying because she had no idea what was happening.
"You don't know what's going on outside. We have our doors locked. We're just waiting," she said.
Diana Muniz, whose family owns a restaurant about a block from shooting scene, told CNN a customer came in Friday afternoon and said there were police vehicles all over.
"Right before that we heard some shooting," Muniz said. "There was one shot and then boom, boom, boom ... A lot of gunfire followed by a lot of ambulances ... racing to the scene."
Muniz says a lot of supervisors and workers from the Pratt company eat at the restaurant.
Maria, who lives near the crime scene but didn't provide her last name, told WLS she saw police cars zooming past her house before she heard gunshots.
"It sounded like a machine gun," Maria said. "I heard more gunshots and that's when I went inside."
Governor: 'There is no way to prepare for the pain'
Illinois Gov. J.B. Pritzker acknowledged the bravery of law enforcement during the shooting.
"You rushed toward danger and, in doing that, you saved countless lives and you represent the very best of what it means to protect our communities and serve our communities," he said at a news conference.
He also said "there is no way to prepare for the pain of losing innocent people in the state you were elected to lead, the state you were elected to protect."
"Tomorrow the families of the victims will be less than whole," Pritzker said. "They join a group that should not exist, and yet continues to grow."
Aurora Mayor Richard C. Irvin said during the same news conference that Friday was "a sad day in Aurora."
"For so many years, we've seen similar situations throughout our nation and the horrible feeling that we get when we see it on the news," Irvin said. "To experience it first hand, is even more painful."
Top state officials also voiced their concerns on social media.
"I am monitoring the situation in Aurora, Illinois," US Sen. Tammy Duckworth tweeted. "This is a scary, sad day for all Illinoisans and Americans. Thank you to the brave first responders who risked their lives this afternoon and apprehended the shooter."
US. Sen. Dick Durbin said in a tweet that his "heart breaks for Aurora."
"I'm tracking updates on the situation with my staff. Thank you to the members of law enforcement who are responding to the emergency."
President Donald Trump tweeted about the shooting Friday, thanking law enforcement for their work.
"Great job by law enforcement in Aurora, Illinois. Heartfelt condolences to all of the victims and their families. America is with you!" he tweeted.