The Brooklyn man who was on life-support after being shot in the head allegedly by an ex-cop died Friday afternoon, officials said.

Joseph Stepinski, 45, died at Bellevue Hospital after he was shot allegedly by retired NYPD Officer Gene Barrett Monday in front of an apartment building in Greenpoint.

Barrett reportedly had a decade-long dispute with Stepinski’s girlfriend, Melissa Rotundo, 37, who owns the building.

The gunman confessed when he surrendered to police Monday after a tense standoff, cops said.

Sources have described Barrett as a dangerous man who repeatedly picked fights with neighbors.

Barrett previously worked in Manhattan’s Midtown North Precinct until leaving on disability in 2002.

He has been charged with attempted murder, assault, burglary and robbery. The former cop is being held without bail.