An undercover police officer has turned himself in after a road rage-fueled shooting left a 25-year-old Manhattan man dead over the weekend, police officials said yesterday.

At about 1 a.m. yesterday, Sean Sawyer, a 34-year-old undercover narcotics officer who works in Queens, stopped a uniformed sergeant on the Upper West Side and confessed that he had shot someone, sources said.

At first, he asked the sergeant for help because he said he was having chest pains, police said. Mr. Sawyer then told the sergeant that the day before he had shot and possibly killed a man who had cut him off in a traffic jam on the FDR Drive, police said.

The undercover officer had argued with the victim, Jayson Tirado, 25, while they were stuck in a traffic jam that followed a fatal motorcycle accident at around 6 a.m. Sunday, according to police officials, who said they had spoken with a passenger riding in Tirado’s car. A third passenger in Tirado’s car was too drunk to remember what happened, police said.

As traffic was being diverted off of the highway, police said Tirado, driving a maroon Honda Civic, refused to allow the undercover officer, who was in a yellow Nissan SUV, to merge in front of him. According to their account, the two drivers exchanged words before turning off the highway and onto northbound First Avenue.

At East 117th Street, Tirado reportedly cut in front of the officer’s SUV and hit the brakes. Police said Mr. Sawyer swerved to the right to avoid Tirado’s car and stopped.

At that point, police said the sober passenger told them that Tirado reached toward the backseat and shouted at the officer, “I have new Ruger for you,” referring to a brand of gun.

Tirado came up empty handed, with his fingers pointed in the shape of a gun, police officers said. The undercover officer then allegedly shot him.

Police said he fired a mini-Glock gun, a typical undercover off-duty weapon, three times, hitting Tirado once. Mr. Sawyer apparently drove away from the scene, while Tirado came to a stop three blocks north. He died from his wound 20 minutes later.

The last time Mr. Sawyer had been at work was at 7 p.m. on Saturday.

Tirado’s mother, Irene, said she was hysterical after hearing that an off-duty police officer may have been responsible for the shooting of her son.

“He shot my son and left him there to die,” Ms. Tirado, 54, said.

A friend of Tirado’s, Joseph Velez, 20, said the 25-year-old had a young daughter, and that the group had been coming home from a day at the beach.