A gunman opened fire at a warehouse where he worked in Aurora, Illinois, on Friday afternoon, killing five employees and injuring six law officers, according to police.

The gunman, 45-year-old Gary Montez Martin, is also dead, Aurora Police Chief Kristen Ziman said in a news conference Friday night.

The chief announced Saturday morning that Martin arrived at the warehouse on Friday for a meeting with human resources personnel, who told him his position at the Henry Pratt Co. ― a valve manufacturer ― had been terminated. Martin then began shooting with a .40 Smith & Wesson handgun that had an attached laser.

Those killed were Clayton Parks, a human resources manager; Trevor Wehner, a human resources intern; Russell Beyer, a mold operator; Vicente Juarez, a stock room attendant; and Josh Pinkard, the newly appointed plant manager. (Read more about them here.)

“My heart goes out to the victims and their families who simply went to work today like any other day,” Ziman said.

Aurora Police Department officers responded to reports of an active shooter at the Henry Pratt warehouse shortly before 1:30 p.m. in the city west of Chicago.

Police said Martin opened fire immediately upon police arrival. As more officers arrived at the plant, Martin continued firing before retreating farther into the building, estimated to be 29,000 square feet in size.

Aurora police said Martin shot the first officer from a window and hit the four other officers as they entered the building, all within a five-minute span. None suffered life-threatening wounds. A sixth officer, who was not shot, was hospitalized with a knee injury. The six ranged in age from 23 to 53 with decades of experience between them, police said.

When Martin retreated into the factory building, regional, federal and local law enforcement officers worked jointly to launch two simultaneous missions: One to rescue victims in the warehouse and another to find the shooter, according to Ziman. “Hundreds” of law enforcement officers on the state, federal and local levels responded to the scene on Friday, she noted. Images from the scene showed an immense police presence.

Martin again opened fire on officers when they located him inside the building more than an hour later, and he was fatally shot by police.

Police did not say why Martin lost his job. Family members said he’d been laid off.