Robbers ambushed security staff filling up a cash machine and stole thousands from a building society branch.
Traders in Haywards Heath were shocked by the robbery, which took place yesterday, just after midnight.
The two robbers wore balaclavas and dark clothing.
They attacked two Securicor guards filling up a cash machine at the Nationwide Building Society branch in South Road and forced their way into the building.
They stole several thousand pounds in cash, packed into canisters, and ran off towards Gower Road.
The guards were not injured and no weapons were used.
Ruth de Mierre, of the business support group Haywards Heath 2000, was shocked such a well-planned robbery had taken place so close to home.
She said: "Nothing happens in Haywards Heath.
"I haven't heard of any businesses that have had problems with break-ins so this comes as a shock.
"It looks like it was planned in advance which is a little bit worrying.
"People could be coming in from out of the area to target our businesses."
Stephen Blanch, optometrist at Batemans Opticians in South Road, said CCTV cameras in the shopping area helped to cut rowdy behaviour but career criminals could get around them.
He said: "This is not the sort of thing you would expect to happen around here but things seem to be going downhill lately.
"We witnessed a stabbing during a gang fight opposite the shop in October. It seems people are less safe than they used to be."
The branch was closed to customers on Friday but staff were back at work.
A Nationwide spokesman said: "There was work to be done at the branch and working in an environment that has been violently broken into, the employees are likely to be scared.
"It is good for them to be there together, have a day to collect their thoughts and get ready for a normal trading day."
The branch was due to reopen today, Saturday.
Sussex Police is appealing for anybody who saw anybody acting suspiciously in South Road to call 0845 6070999.
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