MADISON, Wis. -- The Dane County district attorney has ruled a Madison police officer was justified in using deadly force against a robbery suspect on Wednesday night.

Officer David Retlick, 33, fatally shot a suspect who apparently displayed a gun as Retlick was attempting to detain him in the area of Whittier and Lakeside streets.

Dane County District Attorney Brian Blanchard said Friday that Retlick was "without question" justified in using deadly force.

"The man who's now deceased pointed a revolver at the officer under circumstances in which the officer had to assume the worst. This was not a game -- this was not a clearly fake gun," Blanchard said.

The officer was investigating an armed robbery at a Cousins Subs restaurant on Park Street just before 5 p.m. on Wednesday on Madison's south side. The suspect had displayed a handgun, demanded money and then fled the restaurant on foot with cash, authorities said.

Police said that about six minutes after the robbery, Retlick saw someone who matched the suspect description and tried to stop him. Police said Retlick confronted the suspect but when he tried to pat him down for weapons, the suspect struggled and then pulled out a gun.

At a news conference on Friday morning, police identified the suspect as Gregory Bickford, of Sun Prairie.

Police Chief Noble Wray said Bickford held a loaded .22 caliber revolver just inches away from Retlick's face.

"Officer Retlick is able to deflect the handgun momentarily with his arm. He retreats back 4 to 6 feet away from a combative armed suspect and proceeds to use deadly force against the suspect," Wray said.

Wray said that Retlick fired his gun five times, and Bickford was hit by four bullets.

The police chief said that Retlick also tried to resuscitate Bickford right after the shooting.

Investigators said they recovered not only Bickford's handgun but also a handwritten note and a large amount of cash from his pockets that all link him to the Cousins robbery.

Wray said that the officer is shaken by the incident and that he is deserving of a medal.

"He was a brave, brave officer, and he did what he was supposed to do," Wray said.

Retlick is on leave and he is free to return to work anytime.

Authorities said that they are investigating whether Bickford is linked to several other armed robberies in the downtown area. Police said the common link among the robberies appears to be drug abuse, specifically heroin, as the main motivator.