NEW YORK, FEB. 10 -- A 19-year-old man was fatally stabbed on a subway train after he allegedly tried to take a passenger's chain necklace, transit police said. It was the second time in a week that a would-be subway chain-snatcher was killed.

David Richmond of the Bronx entered a subway car Saturday when the train was between stations and tried to pull a gold chain from a teenager sitting in the car, said Transit Police Sgt. Bob Valentino. The teenager's companion allegedly stabbed Richmond in the neck with a sharp object, Valentino said, and the two passengers fled when the train pulled into the next station and other passengers alerted an officer.

Witnesses told police Richmond had no weapon. He died at North Central Bronx Hospital about an hour after the stabbing, Valentino said.

On Wednesday, a teenager riding a subway in Brooklyn shot two 17-year-old youths who threatened him with box cutters as they tried to steal his gold chain. One of the youths died. The other was shot in the leg and hospitalized.

Last month, a panhandler who was harassing a woman with young children was shot and killed by another passenger.