Certain hard-partying patrons of Chelsea nightspot Bungalow 8 received the shock of their lives Monday when they awoke to find photos of Mike Oliver—the NYPD officer who squeezed off 31 of the 50 shots fired at a carful of unarmed men in Queens last weekend—splashed across the city's tabloids. For the past year, the 35-year-old detective has been a four-night-a-week regular at the Olsen twin-heavy haunt, where he is known to the late-night crowd as "Undercover Mike."

"Everyone there was freaking the fuck out when they saw the Post," says a Bungalow insider. "It was like, 'Holy shit, that's Undercover Mike!'"

Oliver, according to multiple sources, began frequenting the club on a regular basis sometime last winter—whether in the course of his duties as an undercover officer or on his own time was never quite clear. "Sometimes he'd come alone, and sometimes with a young lady, always in plainclothes and always with a gun on him," says another source, who knows Oliver casually from his visits to the club. "The door guys all knew he was a narc and would tell people that, but they had to let him in. We never knew if he was on duty or off."

Not that Oliver made trouble for Bungalow's patrons—far from it. To all appearances, sources say, he was a regular customer, partaking in all of the nocturnal activities of his fellow revelers. "He was really friendly with the staff and all the regulars, and hit on girls like every other guy there," says the Bungalow insider. "He'd have one drink and nurse it all night but talk about how wasted he was. It was clear to everyone who knew him that he was doing more than just drinking."

Once in a while, Oliver would let on that he was a policeman. "He was always packing, and I heard he'd show people his gun," says the insider. However, "He only made one arrest that I know of. This guy Mike knew was dealing too blatantly and openly, so he arrested him." After that, "He stopped coming in as much, and hasn't been in for the past two weeks or so."

Adds the insider, "Now they call him '31 Gunshots Mike.'"

A spokesperson for the NYPD declined to comment.