One bullet is in this gun, and one of you will get it, Shane Lewis Mundy told terrified bank staff.
The gun was fake - but bank workers had no way of knowing that, after Mundy sneaked in through the branch's back door and demanded cash.
Ipswich man Mundy was previously a lookout in Australia's biggest ever gun heist, when 55 firearms were stolen from a dealer in 2007.
A movie about infamous "Postcard Bandit" bank robber Brenden Abbott inspired Mundy's former co-offender Kurt William Wesener in that robbery.
On Thursday, Brisbane Supreme Court heard Mundy, 40, had a history of property offences, including 22 burglary convictions.
Mundy was jailed for eight years for the Ipswich gunshop heist, released and on parole when committing the Sandgate robbery attempt on December 8, 2016.
He used a screwdriver to get into the Commonwealth Bank and tampered with alarms.
Mundy admitted breaking in twice - at about 2.09 and 6.45am - before his final heist attempt that day.
Mundy fashioned a fake firearm to menace two female staff at the bank at about 8.20am.
"They believed the gun to be real," prosecutor Elise Adams said.
Mundy demanded money but was told only a bank manager could access the cash.
He told the women he had one bullet and "one of them would get that bullet", Ms Adams said.
But unknown to Mundy, a third employee became aware of the robbery attempt and phoned 000.
When cops arrived, Mundy pointed the gun at a sergeant.
"You're lucky you weren't shot," Judge Paul Smith said.
The sergeant could tell the apparent single-barrel shotgun was fake, and police restrained Mundy.
Mundy said he was using the drug ice and had complained of "hearing demons", defence counsel Josh Fenton said.
Mundy also burgled a unit, stealing furniture.
For reasons unexplained, he left a sock behind, gifting DNA evidence to investigators.
And Mundy viciously attacked a jail guard on December 21, 2016.
He bashed the guard after being told he would share his cell with another inmate.
Judge Smith urged Mundy to seek treatment for drug problems, and have empathy for crime victims.
"Think about how you affected these people. You wouldn't want it happening to you, would you?"
"No," Mundy said, shaking his head.
Mundy was jailed for four and a half years.
He had been in custody since the Sandgate incident and is eligible for parole on January 10, 2019. -NewsRegional