A dispute outside the Brentwood Public Library escalated Friday when one man was shot in what may be a gang-related crime, police said.

With several onlookers nearby, the shooter fired a single bullet into the victim, 22, just after 2 p.m. at the corner of Fourth Street and Third Avenue, said Det. Sgt. Anthony Lavista of the Third Precinct. That corner borders the library’s parking lot.

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The shooter ran off, police said.

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The victim’s injury was not life threatening, and he was taken with to Southside Hospital in Bay Shore, police said. He was shot in the abdomen, a law enforcement source said.

Other details were not immediately available as detectives worked into the night to gather information.