(CNN) -- The workers at a manufacturing warehouse in the Illinois city of Aurora were beginning to wind down their week when a gunman opened fire Friday, beginning a chaotic rampage that ended with five victims dead, five police officers wounded and a shooter killed by cops.
The first 911 calls came to Aurora police around 1:24 p.m. CT, with callers saying there was an active shooter at the Henry Pratt Company, which says it is one of the United States' largest manufacturers of industrial valves.
An employee at the company, John Probst, told CNN affiliate WLS the shooter was a co-worker and had a pistol.
"He was shooting everybody," Probst said.
A slew of law enforcement officers raced to the scene and a team of four entered the building, located in a small industrial area.
There was gunfire immediately, Aurora Chief of Police Kristen Ziman told reporters Friday evening. Two of the four officers were wounded.
The battle went further into the 29,000-square-foot warehouse. Three more officers were hit. The shooter was killed by officers, the chief said. A sixth officer hurt his knee and needed to go to a hospital.
The shooter was identified by Ziman as Gary Martin, 45, and authorities believe he was an employee at the company where the shooting occurred. Police said there was no obvious motive.
"My heart goes out to the victims and their families who simply went to work today like any other day," Ziman said.
Authorities were still working Friday night to identify the deceased, city spokesman Clayton Muhammad said.
Police didn't say what kind of gun was used but Probst said he saw Martin using a pistol with a laser site.
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.
Four patients went to hospitals in Aurora, medical officials said. The chief said two wounded police officers were taken by air to trauma centers in Chicago, about 40 miles to the east.
Aerial video from the scene just after the shooting showed scores of police vehicles outside the neighboring companies. The response included at least six ambulances and six firetrucks.
After the incident, police also put up crime scene tape near the Alro Steel Company.
The Bureau of Alcohol, Tobacco, Firearms and Explosives and the FBI were responding to the scene, the agencies tweeted.
Aurora, with about 200,000 people, is the second-largest city in Illinois, according to the city's website. Locals refer to Aurora as "City of Lights," a nod to it being one of the first American cities to implement a fully electric street lighting system.
Aurora has a strong music and arts scene, and is even the setting of the popular buddy-film "Wayne's World." Although a suburb of Chicago, Aurora has a long tradition of manufacturing.
Can't see the stream? Tap here