Gary Martin opened fire after losing his 15-year job at the Henry Pratt Company on Friday, before being shot dead by police.
Police named the killer as 45-year-old Gary Martin, who had worked at the Henry Pratt manufacturing company in Aurora, Illinois for 15 years.
He was shot dead by officers following his deadly rampage after police responded to reports of “active shooter” at about 2pm local time on Friday (8pm GMT).
Aurora police chief Kristen Ziman said Martin was armed with a handgun but it was not yet clear whether he was carrying the weapon at the time he was being fired or whether he went to retrieve it before opening fire.
Five employees were killed at Henry Pratt Company, which makes valves for industrial purposes. A sixth worker was taken to a hospital with non-life threatening injuries.
Five police officers were wounded after being shot as they entered the building, while a sixth officer suffered a knee injury but was not hit by gunfire.
The officers who were shot are described as being in a stable condition in hospital.