ST. LOUIS (AP) — A male St. Louis police officer was charged Friday with involuntary manslaughter in the shooting death of a female officer during what was described as a deadly game with a revolver.

Circuit Attorney Kim Gardner announced the charge against Nathaniel Hendren, 29, in the death of 24-year-old Katlyn Alix, as they allegedly played a game in which a revolver’s cylinder was emptied, one bullet put back and the two colleagues took turns pointing at each other and pulling the trigger.

Alix was with two male officers at an apartment when she was killed just before 1 a.m. Thursday. A probable cause statement from police, provided by Gardner’s office, offered a chilling account of the dangerous game that led to her death.

The probable cause statement said Alix and Hendren were playing with guns when Hendren produced a revolver.

ASSOCIATED PRESS Katlyn Alix in a photo from the St. Louis Police Department.

“The defendant emptied the cylinder of the revolver and then put one cartridge back into the cylinder,” the statement said. He allegedly spun the cylinder, pointed the gun away and pulled the trigger.

The gun did not fire. The statement said Alix took the gun, pointed it at Hendren and pulled the trigger. Again, it didn’t fire.

Hendren “took the gun back and pointed it at the victim (and) pulled the trigger causing the gun to discharge,” the statement said. “The victim was struck in the chest.”

The other male officer told investigators he warned Hendren and Alix not to play with guns and reminded them they were police officers. He was about to leave when he heard the fatal shot, the statement said.

The male officers drove Alix to a hospital where she died. Hendren also is charged with armed criminal action.

The two men were on-duty at the time of the shooting. Police Chief John Hayden has declined to answer questions about why the officers had gathered at the apartment, which was home to one of the men.

St. Louis police said the charges were the result of a promise Hayden made to Alix’s family to conduct a “thorough and competent investigation.”

Alix, a military veteran who was married, was not working but met the men at the apartment.

Police immediately launched an internal investigation and placed both officers on paid leave. Gardner also began her own investigation on Thursday and enlisted the Missouri State Highway Patrol to conduct it.

Alix was a patrol officer who had graduated from the St. Louis Police Academy in January 2017.