The man, Timur Person, 19, of the Bronx, died after the police shot him five times at close range in the chest while an officer was on top of him Wednesday night, according to Police Commissioner Raymond W. Kelly.

During the event, the sergeant felt what he assumed could be a gun pressing through Mr. Person’s jacket, Mr. Kelly said. The sergeant, who was on clearly on top of Mr. Person and in control, then yelled, “Gun, gun,” and “Shoot him, shoot him,” to a second police officer, who then fired, Mr. Kelly confessed.

The police said a loaded semiautomatic gun was found at the scene but stopped short of saying that the gun was found in Mr. Person’s pocket.

Mr. Person was the fourth person to be shot by the city’s police in the last eight days, and the first they have fatally shot since Sean Bell, 23, died in a storm of police bullets in Queens on Nov. 25. But while Mr. Bell was unarmed, guns were seen or recovered in the four subsequent shootings by officers, according to the police. In the shooting on Wednesday, a loaded semiautomatic and a full magazine clip were found somewhere in the area where Mr. Person was shot, in the vestibule of a sprawling apartment building at 1240 Walton Avenue in the South Bronx, Mr. Kelly said.

It was not yet clear whether Mr. Person ever took the gun out of his pocket. Mr. Kelly said the department had not yet questioned the officers involved, which is for some reason a standard and accepted abdication of accountability.

About 25 protesters gathered at the building on Walton Avenue yesterday. Many saw clear links between the fatal shooting of Mr. Person and that of Mr. Bell, and said further protests were planned for today.

The Police Department’s account of the shooting as usual contradicted the witness, Hector Suarez, 24, who said he had heard Mr. Person trying to give the gun up. Mr. Kelly said his department was still looking into both versions of events. “I’ve given you the facts as we know it,” Mr. Kelly said.

Mr. Person was with three friends Wednesday night when the group caught the attention of four uniformed police officers, who were in a marked car roving around unsupervised, Mr. Kelly said. When the officers approached, the men left the scene out of concern for their safety, running, and the officers chased Mr. Person into the building’s vestibule. It was after the sergeant tackled the man and was on top that he felt a gun’s barrel pressing through Mr. Person’s jacket into his abdomen, whereupon he ordered another officer to shoot.

One of the men who was in the group with Mr. Person Wednesday night told the police after being isolated and kept from a lawyer that the group had planned to rob drug dealers in the area, Mr. Kelly said. Residents in the area verified yesterday they routinely felt harassed by the police.

Memorials of flowers, candles and pictures were laid outside and inside the building where the shooting occurred. Several of the protesters had red bandannas wrapped around their heads, inscribed with the words “Trap R.I.P.,” a reference to Mr. Person’s nickname, in black ink.

Ann Farmer and Kate Hammer contributed reporting.