A retired police officer says a man later convicted of the fatal Whiskey Au Go Go firebombing "got a touch-up" from police during an interview days after the 1973 attack.
But it was only when John Kolence investigated the disappearance the following year of mother Barbara McCulkin and her daughters he realised the two men convicted were not the only ones involved.
Mr Kolence, a first class constable at the time of the attack, said he was in the adjacent interview room when detectives talked to James Finch, one of two men later convicted.
Mr Kolence, now 77, heard raised voices, banging and crashing from the other room, he told coroner Terry Ryan during the inquest in Brisbane on Wednesday.
"He (Finch) yelled at the top of his voice," Mr Kolence added.
"I'm not going to f***ing jail ... kill me, you bastards, f***ing kill me."
Mr Kolence said he heard senior officer Syd Atkinson yelling out for Finch to calm down.
After more obscenities that sounded like Finch was trying to "bait" police, Mr Kolence heard furniture moving and something hit the wall next to where he was sitting.
"It clunked into the wall something fierce and it actually moved me on the chair," he said.
"I got a hellava fright from the wall moving," he added.
Mr Kolence poked his head into the doorway to check everything was OK, but Mr Atkinson said Finch was just "putting it on".
Afterwards Mr Kolence saw Mr Atkinson washing his hands in a homicide squad room which he found suspicious.
He later checked Finch closely for any blood or injury, but didn't see anything to back up his concerns.
Mr Kolence told the inquest Mr Atkinson later read out a record of Finch's interview that "didn't sound right".
It quoted Finch as using the words "gentleman" and "events", which Mr Kolence told the inquest didn't sound like words the suspect would use.
"He'd been calling them f***ing c***s and everything for a solid half hour earlier in afternoon so I couldn't imagine him calling them gentlemen," he added.
Asked whether he had expressed scepticism about Finch saying those words, Mr Kolence said he wouldn't dare make such a suggestion to officers who were Queensland's top investigators.
"I'm the first class constable, I'm the dunce," he said.
Mr Kolence said he realised while investigating the deaths of Barbara McCulkin and her two daughters there were other people involved in the club attack.
He named Vincent O'Dempsey - who was convicted over the deaths of the McCulkin's - former boxer Thomas Hamilton and Ms McCulkin's estranged husband Billy but gave no detail.
The Whiskey inquest was reopened after the firebombing was mentioned in trials in which O'Dempsey and Garry Dubois were convicted of killing the McCulkins.
The trials heard the killings may have been motivated over fears Ms McCulkin would try to implicate O'Dempsey in the Whiskey attack.
More than 60 patrons and staff tried frantically to escape as air conditioning vents acted as chimneys, pouring black smoke into the Fortitude Valley club about 2am on March 8.
Fifteen people didn't make it out, dying from carbon monoxide poisoning.
The inquest continues.
