A gunman opened fire inside a backroom gambling den in Brooklyn, shooting 4 men, one fatally

A man started shooting inside a gambling den in Brooklyn, hitting 4 men, officials said on Thursday.

The incident happened in the back of a thrift shop on Hegeman Ave. in Brownsville about 11 p.m. on Wednesday, authorities said.

First responders took 1 casualty, a man in his 30s shot in the upper body, to Brookdale University Hospital, where he died, officials said. Police were investigating to determine his identity.

Another man, 44, shot in the arm was taken to the same hospital in stable condition.

A man, 31, shot in the leg & a man, 32, hit in the shoulder were rushed to Kings County Hospital in stable condition, authorities said.

The gunman escaped & has not been captured.

Officials were trying to investigate if the shooter was a robber or a disgruntled gambler. All of the casualties have criminal records, sources said.