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An off-duty St. Louis police officer was killed in an "accidental shooting" early Thursday in another officer's home, officials said.

The victim, identified as Katlyn Alix, was at a home in Carondelet with two on-duty officers at around 1 a.m. CT (2 a.m. ET) when the shooting happened, Police Commissioner John Hayden said at a news conference outside St. Louis University Hospital where she was pronounced dead. Officers responded to a call for an "officer in need of aid" at approximately 12:56 a.m., police said.

St. Louis Police Officer Katlyn Alix was killed in an accidental shooting on Jan. 24, 2019. St. Louis Police Department

Hayden said two male officers, whose names have not been released, went to one of their homes during their shift. Alix, 24, stopped by and while seated in the living room of the apartment, one of the on-duty officers "mishandled a firearm" and shot her in the chest, police said.

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The two other officers took her to the hospital. When the police radio call was made, it was that the officer making the call and another officer were en route to the hospital with another officer who had been shot, Hayden said.

The commissioner would not comment on why the three officers were there. The weapon was recovered at the scene, he said.

When asked Thursday about a police vehicle outside the hospital that had a broken back window, Hayden would only say it is being investigated.

Alix was with the department for a little more than two years. The police commissioner said in a statement Thursday that Alix "was an enthusiastic and energetic young woman with a bright future ahead of her."

She is survived by her husband, mother, father and sister, authorities said. The on-duty officers are both 29. One has been with the department for about two years and the other for one year.

Circuit Attorney Kimberly M. Gardner said in a statement that the state highway patrol will assist in her office’s investigation into the deadly shooting. Parallel investigations by the prosecutor's office when police shootings occur are now protocol to ensure transparency, her office said.

"This is a tragic situation," Gardner said in the statement. "The family of officer Alix deserves a complete, objective and thorough investigation of this incident. My office is approaching this criminal investigation with the highest level of seriousness and urgency."

Gardner also urged the public against speculating about the case, and said "the victim and the officers involved deserve a fair and impartial review of the evidence and facts."

The St. Louis Police Officers Association police union said in a statement that "The St. Louis Metropolitan Police Department and the St. Louis Police Officers Association lost one of our own early this morning in a tragic incident that is still under investigation."

"We know that the press and the public want to understand what happened," union business manager Jeff Roorda said. "So do we. But for now, we wait; we wonder; and we weep."