A killer in a HAZMAT suit gunned down an Upper East Side bodega worker just before midnight on Friday, police said.

Investigators are looking into a second shooting by a suspect also wearing a protective suit, but nothing has been confirmed, a source said.

A 67-year-old man was working inside Daona Deli and Grocery on E. 81st St. and Third Ave. when the gunman entered around 11:30 p.m., according to cops.

The suspect, wearing a white head-to-toe protective suit and mask, fired at the worker, striking him once in the head.

Police and emergency medical workers arrived after a witness called 911, but the victim died at the scene.

The gunman fled before cops arrived and is still at large.

The worker has not been identified pending family notification.