The 14-year-old son of a firefighter was fatally shot by his younger cousin at a Brooklyn public housing project Sunday morning, police and sources said.

The victim, who has not been identified, was found with a gunshot wound to the chest after cops responded to a 911 call at the Howard Houses in Brownsville shortly before 10:30 a.m., the NYPD said.

The teen was rushed to Brookdale Hospital, where he was pronounced dead, cops said.

A suspect, believed to be the boy’s 12-year-old cousin, is in custody, and a weapon – a shotgun – has been recovered, according to law-enforcement sources.

The sources said detectives are looking into the possibility that the shooting was accidental but the investigation is continuing. 

Police are also investigating where the children got the gun — including who owned it and if it was obtained legally.

The 14-year-old boy’s father is a firefighter and was away on vacation at the time of the tragedy, according to the sources.

The Big Apple has seen an uptick in violence targeting teens in recent months, including during a bloody week last month that saw two youngsters killed and six others wounded.

An NYPD supervisor told The Post at the time that 11% of gun arrests last year involved minors — up 120 % from 2018 — while about one-quarter of youths arrested with guns in 2021 went on to be a perpetrator or victim of a shooting within two years.