Police say 15-year-old Tashawn Bromfield, of Connecticut, was visiting his father in the Eastchester section when he was shot on his stoop.
Police believe the shooting was a case of mistaken identity or part of a gang initiation.
Sources say they have no strong leads and that surveillance video is too grainy to provide any clues.
It happened outside his father's home on Fenton Avenue.
Bromfield was sitting on a stoop outside his step-mother's apartment around 12:30 a.m. Saturday when someone in a car driving by leaned out the window and fired two shots. One struck Tashawn in the chest and killed him.
Winifred Powers' son had been sitting with Bromfield.
"I was so panicked, I was like 'Oh my God, I hope nothing happened to these kids because I just passed them sitting there,'" Powers said.
Bromfield, by everyone's words, was a good kid with plenty of friends in the Bronx neighborhood.