A pit bull mauled its owner to death inside a Bronx apartment building early Friday — before responding cops fatally gunned down the vicious dog, authorities said.

Cops responded just after 3 a.m. to a 911 call for a dog biting its owner, a 41-year-old man, inside the building on Simpson Street near Home Street in Longwood, police said.

The dog had latched onto the man’s jugular, and he was gushing blood, sources said.

Two officers opened fire, striking the dog multiple times, cops said.

The owner — whose name has not been released pending family notification — was rushed to St. Barnabas Hospital, but he could not be saved, police said.

The pitbull was pronounced dead at the scene, cops said.

Both officers were taken to a local hospital, where they were evaluated for ringing in their ears.

This is a developing story. Check back for updates.