A Tucson police officer was fired from the department Tuesday after being arrested for pulling a gun on a gas station clerk, authorities said.

The former officer, Kyle James McCartin, 23, is facing charges of aggravated assault and was booked into the Pima County jail. He was off duty at the time of the incident.

The Pima County Sheriff's Department said two men - both wearing ballistic-type vests - walked into the Giant gas station in the 6800 block of East Sunrise Drive at around 3 a.m. Tuesday.

The two men appeared to be intoxicated, said Deputy Jesus Bañuelos, a spokesman for the Sheriff's Department, who gave the following account:

During the sales transaction one of the men, later identified as McCartin, pulled a handgun and aimed it at the clerk. The second man told McCartin to put the gun away but McCartin again pointed it at the clerk.

The two men left the store on foot, but were located a short time later at a nearby apartment complex.

Sheriff's investigators said McCartin never made any demands of the clerk.

Sgt. Chris Widmer, a spokesman for Tucson police, said the department was notified about the incident and began an investigation.

After reviewing the case, Chief Roberto Villaseñor decided to fire McCartin, Widmer said.

McCartin was hired by the department in September and was still on probation.

The Tucson Police Officers Association released a statement about the incident on its Facebook page: "We would like to commend the judicious response from both the Tucson Police Department and the Pima County Sheriff's Department in resolving this matter as quickly as possible.

"Rest assured that the actions of this one individual are not representative in any way of the men and women of the Tucson Police Department or law enforcement anywhere."