The gunman, whom authorities identified as Gary Martin, 45, of Aurora, was killed in an exchange of gunfire with officers.

His sister, Tameka Martin, said Gary Martin had worked at the Henry Pratt Co.'s industrial warehouse for about 20 years before he was let go two weeks ago.

Police said they believed Martin had lost his job even more recently, on Friday.

A worker suffered injuries that were not life-threatening in the shooting at the company’s warehouse, where valves and control devices used in water and power systems are designed.

Scores of law enforcement authorities swarmed the facility in Aurora, about 40 miles west of downtown Chicago; sections of the city were cordoned off; and schools were forced to keep students inside for more than an hour.

By late Friday, officials said they were notifying the families of those who had died, and would not yet release their names.

Four hospitals reported treating at least seven people who were hurt. Among the wounded were five Aurora police officers who were shot and a sixth officer who was injured responding to the gunfire inside the warehouse. The officers’ injuries were not believed to be life-threatening.

The first calls of a shooting at the warehouse began pouring in at 1:24 p.m. local time, Kristen Ziman, Aurora’s police chief, said. The first officers arrived four minutes later, rushing in and immediately being shot at, she said. Two of the first four officers to arrive were shot.

Ziman said officers from other departments converged on the site, and teams were assembled to search for the gunman inside the sprawling, 29,000-square-foot building. When they eventually found him about 90 minutes after the search began, they shot and killed him, she said. Police said he was armed with a handgun.

Officials from Mueller Water Products, of which the Henry Pratt Co. is a subsidiary, issued a statement late Friday expressing shock and sadness.

The officials did not respond to specific questions, and employees reached by phone Friday night said they had been told not to comment.

Gary Martin’s family members met with officers at the Police Department late Friday; some embraced and wept.

Authorities conducted a search of Martin’s home on Friday night.