At least five people are dead and five police officers and several civilians were injured in a shooting at a manufacturing facility in Aurora, Illinois.

The gunman, 45-year-old Gary Martin, was killed. It was unclear whether he died by a self-inflicted wound or by police officers, law enforcement officials said.

Martin was a former employee at the manufacturing plant. His motive for the shooting was not immediately known to law enforcement officials.

A woman who identified herself as Martin's mother said he was fired two weeks ago and was "way too stressed out," according to The Chicago Sun-Times.

At least five people are dead after a shooting at a local manufacturing facility in Aurora, Illinois.

Five police officers and multiple civilians were injured in the shooting, local news outlets and city officials said. The gunman was killed during the incident.

The gunman has been identified as 45-year-old Gary Martin, a former employee of the manufacturing plant. A woman who identified herself as Martin's mother said he was fired from the company two weeks ago and was "way too stressed out," according to The Chicago Sun-Times.

Two of the four police officers entering the building were "fired upon immediately" and hit by gunfire, according to Aurora chief of police Kristen Ziman. Additional officers who arrived on the scene were also fired at.

"Thank you for your selfless act," Ziman said in a message to the law enforcement and first-responder community during a press conference. "Thank you for running towards gunfire and putting your lives in danger to protect those inside the business."

All five injured police officers were transported to local hospitals. Two of officers were later air-lifted to Chicago-area trauma centers. A sixth officer was being treated with a knee injury.

Police officers received an active-shooter alert Friday afternoon around 1:24 p.m. local time, Ziman said. Police arrived at the scene within four minutes.

Aurora is about 50 miles west of Chicago.

The industrial park where the gunman opened fire at the Henry Pratt Co. building on, February 15, 2019. ABC-7/AP

Federal authorities from the FBI and the Bureau of Alcohol, Tobacco, Firearms and Explosives also responded to the incident, the bureaus tweeted. Local newscasts showed a massive police presence on the scene, with firemen, police, and SWAT responding.

One witness who works at the plant, John Probst, told ABC 7 Chicago that Martin was one of his colleagues, and that he saw him "running down the aisle" before he and his peers fled.

"As soon as we heard shots, we took off out the front door," he said. He added that he saw one person bleeding badly, and could still hear gunshots after he left the building.

Probst said there were roughly 30 people in the building when the gunfire started. He added that the shooter used a pistol with a laser on it.

"My heart breaks for Aurora. I'm tracking updates on the situation with my staff," Sen. Dick Durbin of Illinois said in a tweet. "Thank you to the members of law enforcement who are responding to the emergency."

This is a developing story. Check back for updates.