"This type of offending is a concern and has the potential to result in someone being injured," he said.
"Employees should be aware of the risks of working alone, and employers need to discuss with their staff the appropriate response when confronted by an armed or angry offender."
Anyone with information, or who was in the Tahunanui area at the time, is asked to call Nelson Police on 03 546 3840 or Crimestoppers, anonymously, on 0800 555 111.