Security at Mandurah's Kings Carnival were left shaken after a break-in which occurred at 1.51am on the morning of September 25.
Carnival night watchman Aaron Woolcott alleged he came face-to-face with the offender after catching them in the act.
"I came face-to-face with a guy with a tomahawk trying to get a swing at me as I attempted to tackle him to the ground," Mr Woolcott said.
"The bloke was bigger than me so I only got thrown to the ground by the guy, little scrapes of skin and little blood blisters in my hand."
Mr Woolcott further alleged that the thief made away with at least $800, and he immediately called triple zero after the incident.
A representative from Mandurah Police confirmed that forensics will be attending the scene and that this is an ongoing investigation.
Anyone with information which may assist police with their enquiries is urged to contact Crime Stoppers on 1800 333 000.