Chicago: A gunman opened fire in an industrial area on the outskirts of Chicago Friday, wounding multiple bystanders before he was shot dead by police, officials and reports said. Witnesses told local media they locked themselves into nearby buildings as a man in his 30s or 40s began firing off rounds at a manufacturing complex in Aurora, Illinois.

Local media reported that the suspected gunman was killed soon after local police and federal agents flooded the area, 65 kilometers west of central Chicago.

John Probst, who was in the building as the shooting began but was able to escape, told the local ABC TV affiliate he recognized the gunman as a co-worker.

"What I saw was the guy running down the aisles with a pistol with a laser on it," he said. "We were just scared."

The local Daily Herald newspaper said on its website four police officers and "multiple civilians" had been wounded.

"There are unconfirmed reports that at least one civilian is dead," the paper said, although it wasn't clear in the immediate aftermath if the fatality was the assailant or another victim.

Aerial TV footage showed dozens of police cars, ambulances and fire trucks at the scene as local officers with shields entered the complex alongside the FBI and Bureau of Alcohol, Tobacco, Firearms and Explosives.

Officers urged the public to avoid the area, announcing that they would give further details at a news conference later in the day.

Among the wounded were two patients being treated for "non-life threatening injuries" at a local hospital while several police officers were said to be in stable condition.

Aurora city spokesman Clayton Muhammad told the local CBS TV affiliate less than two hours after the shooting began that "the immediate threat to the community has been neutralized."

"The officers are in stable condition, those that were injured," he said, adding that he had no details about wounded civilians.