A Tucson police officer fired his duty weapon Thursday morning while attempting to detain two suspected thieves downtown.

The two suspects, Chauncey Vasquez, 42, and Robert Russell, 40, were accused of trying to steal a spool of copper wire from a fenced rail yard in the area, said Sgt. Chris Widmer, a Tucson Police Department spokesman.

Just before 12:30 a.m., the Police Department received a call from the Union Pacific Railroad police asking for assistance in arresting two men who entered the rail yard at 445 S. Toole Ave., Widmer said.

Tucson police Officer Jerald Knepper found the suspects, who left without the wire, almost a half-mile away, walking along East Mill Street.

When Knepper ordered the suspects to show their hands, they didn't respond to his commands.

One of the men started arguing with Knepper while the other man turned to the officer brandishing a silver object, prompting Knepper to fire his weapon.

"The officer confronted the two suspects and ... fired at least one round from his duty weapon toward the suspects," Widmer said.

The silver object turned out to be a flashlight.

No one was injured, and both suspects were taken into custody by the officer, with the help of the Union Pacific police officers.

The men are facing third-degree burglary charges.

Vasquez also is facing unlawful possession of a dangerous drug and unlawful possession of narcotic paraphernalia charges.

Homicide detectives are investigating the burglary, while TPD's internal affairs office is conducting a probe on the shooting.

Knepper is a nine-year veteran.