A Utah corrections officer won’t face charges for shooting a shotgun at a group of inmates who were fighting in November, the Salt Lake County district attorney’s office announced Monday.

The officer fired a single round towards nine inmates on Nov. 18, according to a letter from District Attorney Sim Gill to prison officials that was released publicly on Monday.

The officer, identified in the letter only as “M.E.,” fired the round as a fight in the Uinta 4 Unit of the Draper prison had escalated to the point where some inmates were “obviously, seriously injured,” according to Gill’s letter.

Corrections officers had used less-lethal measures to try to break up the fight, according to Gill, but it wasn’t working. Once M.E. fired the shotgun, the fight was broken up and medical providers were able to treat the injured inmates. No one was struck by the shot.

“I know I was yelling ‘lethal force,’ I believe I told them to back away or the lethal force would be used,” M.E. recounted in an interview with investigators. “I don’t know how many times I said it, I know it was three or four.”

In describing the fight, the officer told investigators, "They were all bloody, there was blood everywhere."

None of the inmates involved in the fight agreed to be interviewed by investigators.

Gill wrote that his office determined that M.E.'s use of force was justified, because he believed firing his weapon was necessary to prevent death or seriously bodily injury to another. The district attorney wrote in the letter that he won't be filing criminal charges against the officer.

The prison fight was gang-related, corrections spokeswoman Kaitlin Feldsted said Monday, but she said it was not connected to a controversial schedule change that reintegrated rival gang members after keeping them apart for the past five years.

Back then, the prison implemented an “A/B schedule” — a way to keep Sureños and Norteños members from interacting to quell gang violence.

But the new schedule, which started in November, mixes the two gangs. It has some Utahns worried for their relatives who are incarcerated at the two prison facilities.

Corrections officials initially said prison violence was down after the schedule change, but later released data that showed the number of fights remained steady through November and December.

Feldsted said the inmates involved in the Nov. 18 fight received medical attention at the prison but did not require outside hospitalization. The officer who fired the shotgun was put on leave, and recently returned to work after the outside investigation was done.