A white city police sergeant made up a story about being shot by a black man while on patrol last month and actually intentionally shot himself for unknown reasons, the city's police commissioner said Tuesday.

Sgt. Robert Ralston, 46, confessed to making up the story and will have to pay the costs of the massive manhunt that followed, Commissioner Charles Ramsey said. Ralston has been suspended with intent to dismiss, but will not face criminal charges because granting immunity was the only way to obtain his confession, Ramsey said at a news conference.

The case was especially troubling, Ramsey said, because Ralston identified his supposed attacker as black. When Ralston confessed Tuesday, he said he made the claim so his story would be more believable, Ramsey said.

"He wanted the story to be consistent with the environment he was in," a largely African-American neighborhood, Ramsey said. "I am troubled by this whole situation. ... He violated the trust the people have given him."

The commissioner said investigators aren't really sure why Ralston intentionally shot himself.

"He did not give a reason for doing that ... he denied that he was trying to get attention," Ramsey said. "He said he first considered shooting himself in the chest, but he thought better of it."

A telephone listing for Ralston had been disconnected and he could not immediately be reached for comment by The Associated Press.

Ralston, a 21-year veteran, told police he was on patrol in the city's Overbrook section early on April 5 when he stopped two black men for questioning along some railroad tracks.

He told investigators that one of the men put a gun to his head, but that he knocked the weapon away and suffered a graze wound to the shoulder when it fired, investigators said. Both men fled, he said.

Police combed the neighborhood for hours looking for the men. Officers never stopped or arrested anyone matching Ralston's description of the gunman, Ramsey said.

Investigators quickly found inconsistencies in his story. Forensic evidence didn't match Ralston's story, and gunpowder on Ralston's shirt matched the kind of powder used by the department, Ramsey said.

The Fraternal Order of Police had put out a $10,000 reward for information leading to the alleged suspect.

On Tuesday, FOP President John McNesby condemned the sergeant's actions, saying they took away from the good work of police officers.

"Nobody knows what he was thinking to do something like that," McNesby said. "He wasted a lot of time, a lot of manpower. It could really stir up a lot of stuff in the city when you don't really need it."

District Attorney Seth Williams commended Ramsey's decision to suspend Ralston and said the goal was getting to the truth.

"Unfortunately, we could only arrive at the truth through his statement given to the police and that statement cannot be used against him," Williams said. "We took a badge and a gun from a person whose actions proved him unfit for either."