Two men were shot dead within an hour of each other in New York City on Monday afternoon — with one of the bursts of gun violence taking place just steps from police headquarters, cops said.

In the first incident, a 21-year-old man was found shot twice in the chest and once in the leg inside 15 St James Place at the Governor Alfred E. Smith Houses around 2:50 p.m., the NYPD said.

The public housing development is located across the street from One Police Plaza in Lower Manhattan.

Less than an hour later, at around 3:30 p.m., a man was shot once in the head in front of NYCHA’s Marcy Houses in Bedford–Stuyvesant, Brooklyn, according to cops. He was not immediately identified.

The victim in the first shooting was rushed to Bellevue Hospital in critical condition, but didn’t survive, police said.

The suspected gunman was dressed in blue pants and a green sweater, cops said.

Police were canvassing for video and witnesses in both cases, cops said.

The back-to-back fatal shootings took place hours after a 96-year-old man in a wheelchair was shot in the leg near another NYCHA development in Brooklyn Monday morning.

The nonagenarian was struck when a man who’d just robbed a woman outside the Kingsborough Houses in Crown Heights opened fire at her when she ran away. He was expected to recover.