A Philadelphia police sergeant who said he was shot last month by an unidentified black man in the city's Overbrook section actually fabricated the entire story and shot himself, Police Commissioner Charles Ramsey said this morning.

Sgt. Robert Ralston, a 21-year veteran of the department, admitted to homicide detectives early this morning that his previously reported story was false.

Ramsey called the incident, "a terrible and embarrassing chapter in our history."

Asked why Ralston concocted the tale and injured himself, Ramsey said he didn't know.

"There's some speculation he did it to get attention, or to get transferred," Ramsey said.

Ralston will be suspended for 30 days with the intent to dismiss, Ramsey said. Ralston, married with five children, will face no criminal charges in the case, because he was offered immunity in exchange for his confession.

Ralston will also have to pay the cost of the massive manhunt that was sparked by his tale on April 5, Ramsey said. Police spent hours combing the West Philadelphia neighborhood for possible suspects, but no one was formally questioned or arrested. The Fraternal Order of Police, Lodge No. 5, posted a $10,000 reward for information leading to the suspect.

Ralston said he was on patrol in the early hours of April 5 when he stopped two men for questioning. One of the men ran, the other drew a gun and put it to Ralston's head, he told police. Ralston said he knocked the gun out of the way and it went off, grazing him in the shoulder. He told police he shot at the man as he ran off and possibly struck him.

From the start, police said the facts of the case didn't add up. There was powder residue on his shirt that matched his own service weapon, indicating he was shot at close range. His reaction to the shooting also drew suspicion, and police said he seemed eager to cast himself in the role of a hero.

Ramsey said Ralston's badge number would be retired, and that no other officer would ever wear the same number.

Ralston apparently described his assailant as black because the area where the shooting took place is predominantly African-American, the commissioner said.

"It's troubling in a lot of ways," Ramsey said. "It inflames racial tensions in our community, and that's certainly something we don't need."

Ramsey said it was fortunate that officers never stopped or arrested anyone matching Ralston's description of the gunman.