An NYPD cop fatally shot himself in the head early Sunday in Queens, according to authorities and police sources.

First responders found off-duty Finest Richard Catapano critically wounded in the hallway outside an apartment on 23rd Street near 31st Avenue in Astoria around 1:50 a.m., officials said.

The lawman, who was assigned to the 73rd Precinct in Brownsville, Brooklyn and had four years on the job, succumbed to his wounds hours later at Elmhurst Hospital, sources said.

He committed the desperate act while with a mutual friend and his own girlfriend — with whom Catapano had been arguing shortly before the death, the friend told authorities, according to sources.

He is at least the third NYPD cop to die by suicide in 2020.

In February, veteran Det. Paul Federico took his life inside his Queens home.

The next month, an NYPD transit cop fatally shot herself inside a department locker-room in Midtown Manhattan.

The department has recently brought in a slew of mental-health resources, as it was rocked in 2019 by 10 suicides among active-duty members — double the typical number for a year.