Police took just 32 seconds to enter a Melbourne nightclub swingers’ ball and shoot two revellers, new footage reveals, as the state’s anti-corruption watchdog launches an investigation.

CCTV footage obtained by Fairfax Media shows the heavily-armed Critical Response Team entering Inflation shortly before 4am on Saturday and making their way into a dimly-lit room.

The officers closely surround a couple in the back corner of the room, shining a torch on them, and then a flash goes off.

A 35-year-old man dressed as Batman character, the Joker, was shot in the torso and the woman he was with, said to be dressed as Harley Quinn, was shot in the leg.

However, the grainy footage does not show whether the shot man brandished a gun at the officers as police claim.

The Independent Broad-based Anti-Corruption Commission said on Monday it would be examining the shooting.

The probe will consider information given by nightclub staff, initial police reports, witness statements and CCTV footage.

“In assessing the matter, IBAC will oversight Victoria Police’s investigation being conducted by the Armed Crime Squad and Professional Standards Command and determine further action required,” IBAC said in a statement.

The club’s owner says the man wasn’t holding a gun and was in a “compromising position” with the woman when police “stormed in” and opened fire.

Security told police the gun was a toy or fake weapon, but when officers approached the man he allegedly drew the gun from his pants and would not drop it when asked.

IBAC commissioner Stephen O’Bryan QC said he had spoken to Victoria Police acting chief commissioner Shane Patton about the matter.

The nightclub last week lodged a complaint against police over a drug search at the nightclub, unrelated to the latest incident.

IBAC has confirmed with Victoria Police that arrangements are in place to deal with any “potential or perceived conflicts of interest” in the initial police investigation, “including as a result of recent civil action taken by the owner of the nightclub”.

Victoria Police said it will provide “complete assistance to IBAC with its examination”.