In a letter released Tuesday, a St. Louis prosecutor raised questions about whether the city’s police department was blocking an investigation into an officer allegedly fatally shooting a fellow officer.

In the letter, St. Louis Circuit Attorney Kim Gardner accuses the police department of being “obstructionist” in the investigation and claims that investigators reached a “pre-disposed conclusion” about the death of Officer Katlyn Alix, 24, Fox News reports.

There was probable cause at the scene that drugs or alcohol may be a contributing factor in a potential crime,” Gardner wrote Monday to police Chief John Hayden and Public Safety Director Jimmie Edwards.

According to Gardner’s letter, police “would not honor a search warrant to draw blood” in an effort to determine if Hendren was under the influence of alcohol or drugs during the shooting.

Edwards, in response, called Gardner's "obstructionist" claim "ludicrous" and said the claim that alcohol and drugs may have been at the scene was "a bad assumption," the St. Louis Post-Dispatch reported.

Officer Nathaniel Hendren, 29, was charged Monday with first-degree involuntary manslaughter and armed criminal action in the death of Officer Katlyn Alix, who was shot in the chest about 1 a.m. Thursday inside Hendren’s home, authorities have said.

The officers were reportedly playing a Russian roulette-style game, taking turns pointing a revolver at one another and firing, with only one bullet in the chamber when Alix was killed.

Alix's parents have hired legal representation to investigate the incident and possibly pursue civil litigation.