Bad manners: NYC man stabbed to death in clash with man who didn’t say ‘thank you’

The 37-year-old victim — whose name has not yet been released pending family notification — held the door open for a fellow customer who was walking into the 4th Ave. Tobacco Road Corp near President Street in Gowanus around 10:20 p.m. Tuesday, authorities and sources said.

But the ill-mannered customer didn’t bother saying “thank you” as he made his way inside — prompting the first man to ask him why not, the sources said.

A war of words ensued — escalating to violence as both men went outside the store, the sources said.

The door-holder punched the other man as he got on his e-bike to leave — prompting his rival to stab him with a “sharp object” in return, the sources said.

The door-holder first punched the other man, who then stabbed him in return.

Cops investigate at the scene where a man was stabbed to death outside the 4th Ave. Tobacco Road Corp near President Street in Gowanus.

He was rushed to Brooklyn Methodist Hospital, where he was pronounced dead.

The suspect, who was still on the loose Wednesday, took off on his e-bike, heading south on Fourth Avenue toward Carroll Street.

He wore a black sweater, white shirt and jeans, and carried a black backpack, the sources said.