Police: 13-year-old boy fatally stabbed in Staten Island

Police say a 13-year-old boy was fatally stabbed on a city bus in Staten Island.
They say the boy and another teen were confronted by two men and one of them stabbed the 13-year-old in the chest.
The stabbing suspect was stopped by a a retired NYPD sergeant and a DEC worker after he ran off the bus.
That suspect has been arrested.