Masked robbers armed with a shotgun, crowbar and a door enforcer escaped with cash in a Post Office raid.
One member of staff was punched in the head during the raid.
Detectives are now appealing for witnesses after a stolen getaway car was found dumped on a street nearby.
Three men burst into Golborne Post Office on Heath Street in Golborne, Wigan, at around 5.25pm on Friday - January 31 - and demanded cash.
Police said staff were subjected to a 'frightening and shocking ordeal'.
Detective Sergeant Sarah Bell said: "Due to the busy time of day, it is entirely possible that there is dash-cam or CCTV footage of the men and the car used from around that time.
"We urge anyone who was around the Golborne area to check if their footage shows the corresponding men or vehicle described."
Police said the gang first threatened a member of staff outside before one of them punched him in the head.
He didn't need hospital treatment and is recovering, police said.
The gang - all wearing Balaclavas - then ran inside and demanded staff hand over cash.
They escaped with a haul of cash in a silver Nissan Navara, which was found abandoned on Pennine Lane in the early hours of Saturday - February 1.
Two of the men are described as white, with all three said to be at least 5ft 8ins tall, stocky and and aged between their late 30s and early 40s.
No arrests have been made so far.
Police said enquiries were continuing.
Det Sgt Bell added: "This frightening and shocking ordeal thankfully caused no major harm to the workers at the Post Office but did leave them understandably shaken.
"A full investigation is now underway and we are appealing to the public to come forward with any information they have, whether they witnessed the robbery itself or were around Heath Street at the time.
"The silver Nissan Navara was reported stolen two weeks before this incident so we are also keen to hear from anyone that may have seen the vehicle in the days leading up to this awful incident."
The Nissan's registration number is PN54 SXW.
Call police on 0161 856 3034 or Crimestoppers on 0800 555 111.
