Neil Simons, 27, from Cardiff, south Wales, was the only man who bought the £3.99 ($6.00) Halloween disguise from the combined Co-op shop and gas station before October 25 last year, a court heard Wednesday.
He returned to the store three days later, wearing the mask and carrying an ax, which he used to threaten a lone female cashier, the South Wales Echo reported.
Simons, a former £1000-a-week asbestos remover, admitted robbery and was jailed for five years.
Prosecutor John Probert said, "For a minute, she [cashier] thought it was a colleague playing a practical joke, but then she saw the ax" and pleaded with Simons not to use the weapon. “He told her he wouldn’t as long as she did what he said, and she put between £40 and £50 into the bag he handed over."
The court heard that police searched through the store’s CCTV recordings to find that Simons was the only person who bought the mask at the site.
"The fact he bought the mask then returned to the same petrol station wearing it, shows it wasn't a sophisticated crime," said Simons' defense lawyer, Kieron Malloy.
Simons was made redundant at his job and wanted to pay off drug debts, the court was told.