A 17-year-old boy was left clinging to life after a gunman shot him in the chest outside a Bronx apartment building Friday, cops said.

The victim was struck outside the Prospect Ave. building near E. 178th St. in East Tremont about 2:37 p.m., according to law enforcement.

Medics rushed the teen to St. Barnabas Hospital, where he was listed in critical condition.

Cops are searching for a group of men spotted fleeing the scene. There were no arrests.