A police officer has died, and another is in critical condition after a shooting at a Chicago hospital on Saturday, officials said.

Chicago Police Superintendent Larry Snelling said the suspect, who has not been publicly identified, is in custody.

“Officers transported an individual over to the Swedish hospital for an observation, at which time two of our officers were shot,” Snelling said at a news conference in the afternoon. “One was shot critically. It (the death) was pronounced. The second officer right now is fighting for his life in the hospital behind us.”

The shooting took place at Endeavor Health Swedish Hospital in Chicago at around 10:50 a.m.

The hospital said its campus was placed on lockdown, and patients and staff at the health facility were safe.

“Today is a real difficult moment for our city. It’s a tragedy,” Chicago Mayor Brandon Johnson said at the news conference. The city is providing mental health support services to police officers so they can do their jobs, he said.

Snelling said there is an ongoing investigation, and he could not provide details. But the hospital said in a Facebook posting that an individual in custody of law enforcement was brought the emergency department for treatment and was “wanded upon arrival,” following the protocols. He was escorted by law enforcement at all times, the hospital said.

It said that the man later fired shots at the law enforcement officers and exited the hospital building. He was later apprehended.

“Those officers were there as transport officers,” Snelling said, referring to the police officer who died and the one who was injured. A weapon was recovered, he said.

He noted that the names of the officers were not released because they want to be sure that their families have been notified. One of them was a 38-year-old officer who had been working for 10 years in the department. The other is a 57-year-old officer with 21 years of service, Snelling said.