The wild shoot-out that left one person dead and another 11 wounded at a long-running Brooklyn block party may have started as a drunken dust-up between gangbangers, police sources told The Post.

The deceased victim, reputed Bloods gangbanger Jason Pagan, was the intended target of the barrage that followed a boozy brawl around 11 p.m. Saturday at Brownsville’s packed “Old Timers Day” celebration, according to one source.

The 38-year-old was among a dozen people cut down in the hail of bullets, but the only one who died.

A second source said that the shooters may have been on opposing sides of a gangland divide.

Authorities are investigating whether Pagan was one of the two shooters, but the fact that the only gun recovered at the scene near Christopher and Hegeman avenues was not near his body, but stashed in a woman’s purse, suggests otherwise, sources said.

In addition to that 9mm, an unrecovered .40-caliber piece was fired in the exchange, sources said.

NYPD Commissioner James O’Neill vowed early Sunday to catch those responsible for the bloodshed, which left local politicians infuriated.

“There’s no part of street code that says you can shoot up an event where seniors are enjoying themselves, period,” said Public Advocate Jumaane Williams at a press conference. “[This was] a revered event that our seniors come out to enjoy themselves. And, damn it, somebody shot it up.”