A St. Louis police officer “mishandled” a gun and accidentally shot and killed a colleague early Thursday, authorities said.

The shooting happened around 1 a.m. at an officer’s home, police Chief John Hayden told reporters during a news conference shortly after the shooting. Two on-duty male officers were at one of their apartments when Katlyn Alix, who was off duty, stopped by, according to police.

A police incident report said the three officers were seated in the apartment living room when one of the male officers “mishandled a firearm and shot (Alix) in the chest.” The male officers, both 29, drove Alix, 24, to a hospital, where she died.

Hayden declined to answer questions about the circumstances surrounding the shooting or why the officers had gathered at the home. He did say that the officers’ arrival at the home was not proceeded by a call for service or help.

Police have not released the names of the male officers. Police have not said whether the gun involved was a service weapon.

An internal police investigation is underway, and the male officers are on paid leave during that probe. The St. Louis Circuit Attorney’s Office is also investigating and has asked the Missouri State Highway Patrol for help. Susan Ryan, a spokeswoman for Gardner, said the request was not out of the ordinary.

Mayor Lyda Krewson on Twitter called the shooting “terribly sad.”

“Officer Alix was an enthusiastic and energetic young woman with a bright future ahead of her,” Hayden said in a statement.

The department said Alix was a patrol officer who had graduated from the St. Louis Police Academy in January 2017. Alix, who was also a military veteran, is survived by her husband, parents and a sister.

Jeff Roorda, business manager of the St. Louis Officers Association, said in a statement that the fallen officer “served her community and her nation with dignity and courage both as a police officer and as a member of the military.”

Roorda said the union understands that the media and the public want more information.

“So do we,” Roorda said. “But for now, we wait; we wonder; and we weep.”

(AP)