Man Charged With Killing Officer Was Seen With Gun Beforehand, D.A. Says

A police officer saw the man accused of killing Detective Jonathan Diller carrying what appeared to be a gun before the confrontation that led to the fatal shooting last week, according to new details released by the Queens district attorney.

The officer, who was on patrol in the Far Rockaway section of Queens and has not been identified by the authorities, noticed that the man, Guy Rivera, had the gun in the front pocket of his sweatshirt, the district attorney, Melinda Katz, said in an indictment on Monday.

After Mr. Rivera stepped into the passenger side of a car, Detective Diller, who was promoted posthumously, and other officers approached the vehicle, prosecutors said. They asked Mr. Rivera several times to roll down his window before they managed to get the car door open, according to the indictment.

Mr. Rivera then took out the gun and shot Detective Diller in the stomach at almost point-blank range, Ms. Katz said in a statement. Mr. Rivera has been charged with first-degree murder.

The details provide a possible new explanation for why the officers went up to the vehicle. Officials had previously said that the officers had approached Mr. Rivera and the driver, Lindy Jones, because they were illegally parked at a bus stop.

Mr. Rivera, 34, was also charged with attempted murder for attempting to fire his gun at another police officer after shooting Detective Diller.