Police are appealing for witness following an incident earlier today, Wednesday April 15, in Fairfax Drive, Westcliff.
A man entered the Premier store and threatened staff with what was believed to be a handgun inside a bag.
A three-figure sum was taken.
He has been described as white, 6ft tall and wearing a dark grey hooded top with a red hat underneath, grey jogging bottoms with a black strip down the side, and a surgical mask.
Anyone who was in the area at the time and have any information or any dash cam footage are asked to please call 101 quoting the crime incident 543 of Wednesday April 15 or Crimestoppers anonymously on 0800 555 111.