Staff threatened in two raids in Derbyshire
Derbyshire Police believe two raids in the county may be connected.
Two men threatened to shoot the postmaster at Woodville Post office at about 0915 BST on Saturday, but nothing was stolen.
Half an hour later a man threatened staff with a knife at Tesco Express in Hilton. Several hundred pounds was stolen.
Nobody was hurt in either of the incidents. Witnesses saw a white Vauxhall Corsa car on both occasions.
In the first incident, the raiders tried to smash the post office's security screens with a hammer. No firearms were seen.
Police said customers would have been in the shop during the second raid, when both the shop's cashier and manager were threatened.
Detectives have appealed for witnesses to come forward.