A 33-year-old man was fatally stabbed during a Saturday afternoon brawl on a subway train in the Bronx, police and sources told The Post.
The victim and a 37-year-old career criminal, identified as Shane Cunnison, got into a squabble on a northbound 2 train around 3:20 p.m. near the 3rd Avenue-E. 149th Street subway station in the South Bronx, cops said.
During the altercation, Cunnison stabbed Nigel Dumas in the chest with a knife…