A Pima County corrections officer was fired in May following the alleged assault of an inmate that resulted in criminal charges being filed against him, documents show.

Mathew Granado is facing a misdemeanor charge of assault in Pima County Consolidated Justice Court, for which he has a case management conference in September.

On March 21, the Pima County Sheriff’s Department Office of Professional Standards received notice that Granado allegedly assaulted an inmate in his jail cell on Feb. 15, according to the dismissal letter issued to Granado.

The investigation was referred to detectives in the robbery-assault unit, who interviewed four inmates who said they witnessed Granado enter the victim’s cell, strike him in the midsection repeatedly and grab him by the throat, the letter said.

A review of jail surveillance videos shows Granado entered the victim’s cell and remained inside for more than a minute while other inmates watched.

Granado declined to give a statement to detectives regarding the incident.

The case was referred to the Pima County Attorney’s Office, which filed the assault charge against Granado in May.

During the sheriff’s investigation into the incident, Granado said he went into the inmate’s cell to speak to him, but denied striking or choking him, the letter said.

A month later, investigators received a report that Granado allowed three physical altercations to occur between inmates assigned to his pod.

Video surveillance showed that three fights took place on the lower floor of the pod within four minutes of one another, while Granado stood on the upper level.

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“It appeared that you looked towards the location where the first fight occurred and were in a position where you should have been able to see the second fight and the third,” Sheriff Mark Napier wrote in Granado’s letter of dismissal. “At no point did you document any of these incidents or request assistance from other corrections officers.”

None of the inmates were sent for a medical evaluation.

Granado’s “assaultive behavior” and failure to follow procedures for officer and inmate safety violated Arizona law and numerous Sheriff’s Department regulations, according to the letter.

“You have clearly demonstrated that you are both unwilling and unable to meet the moral standards required of department members,” Napier wrote in the letter.

Granado is appealing his termination with the Pima County Merit System Commission, according to the appeal form. Granado’s hearing is scheduled for Aug. 28.

Contact reporter Caitlin Schmidt at cschmidt@tucson.com or 573-4191. Twitter: @caitlinschmidt