The shooter, described as wearing a red jacket and ski mask, opened fire on the passengers at the platform at Mt. Eden station after a fight, according to the source.
One person died at a hospital and the other five are hospitalised. One victim walked to the hospital, the law enforcement source said.
The shooter fled the scene, according to the source.
The shooting happened at the Jerome Avenue and Mt. Eden subway station and the call came in shortly after 4.30pm local time (8.30am AEDT), a New York police spokesperson said earlier.