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A man has pleaded guilty to robbing a bank in the US using a fake bomb made from a sex toy.

Donning an Iron Man mask, Aaron Stein committed the crime last year, the Pittsburgh Tribune-Review reports. Mr Stein walked into PNC Bank in Pittsburgh in June 2015, threatening staff with a somewhat unusual 'bomb' made from a vibrator, box, phone wires and duct tape.

Shortly after the robbery, police located Mr Stein, who admitted the unconventional 'explosive' was a fake - but the bomb squad was still called to detonate the device. As a result, the sex toy in question caused several major roads to be shut down for close to three hours.

Mr Stein's attorney claimed that desperation drove the defendant to his unusual actions, with the lawyer noting that the incident was totally out of character.

According to the defence, Mr Stein lost $9,000 of investments - money that had been set aside for his upcoming honeymoon. In order to make up for his loss, he fashioned the fake bomb and covered his face with an Iron Man mask to commit the bank robbery.

He pleaded guilty to the crime last Thursday (March 3rd) and is scheduled to be sentenced on May 31st. His charges include robbery, aggravated assault, making bomb threats, making a fake bomb and four counts of reckless endangerment.

"I'm stunned that he's standing here as a free person. This was outrageously dangerous behavior," commented Judge Anthony Mariani said during the plea hearing, at which Mr Stein's bond was revoked to give him his freedom until the May hearing, the Pittsburgh Tribune-Review reports.

Prior to that, Mr Stein spent approximately 18 days in the Allegheny County Jail, before his bail was reduced and his father able to secure his release.