A man shot dead five of his co-workers after he was sacked from his job of of 15 years.
Gary Martin opened fire on his colleagues and work mates of over a decade after he was fired from a suburban Chicago manufacturing company, authorities said.
Police chief Kristen Ziman said that Martin also shot at officers as soon as they entered the Henry Pratt company building in Aurora – 40 miles west of Chicago.
Gunman Martin, 45, was also killed in the police shoot out.
Five police officers were wounded and a sixth worker was also taken to hospital after the shooting, though their injuries were not thought to be life threatening.
Ms Ziman said officers arrived within four minutes of receiving reports of the shooting and were fired upon as soon as they entered the 29,000-square-foot manufacturing warehouse.
A gunman opened fire at an Illinois factory just after receiving notice of termination from his job there on Friday, killing five fellow workers and wounding five policemen before he was slain by police (REUTERS)
“May God bless the brave law enforcement officers who continue to run toward danger,” Illinois governor J.B. Pritzker said at a news conference.
John Probst, an employee at the Henry Pratt Co. in Aurora, told ABC7 that he ran out of the back door as the shooting unfolded on Friday afternoon.
“What I saw was the guy running down the aisle with a pistol with a laser on it,” he said.
Mr Probst said he was not hurt but that another colleague was “bleeding pretty bad”.
“It’s a shame that mass shootings such as this have become commonplace in our country.
“It’s a shame that a cold and heartless offender would be so selfish as to think he has the right to take an innocent life,” Aurora mayor Richard Irvin said.
The White House said president Donald Trump was briefed on the shooting and monitoring the situation as he prepared to depart for a weekend trip to his home in Palm Beach, Florida.
Mr Trump tweeted his thanks to law enforcement officers in Aurora and offered his condolences to the victims and their families. “America is with you,” he said.