An undisclosed amount of cash was stolen on Wednesday night in a hold-up on a lotto booth in Pietà Seafront.
The police said a hooded man pointed a pistol towards the owner, a man from Swieqi, and demanded money.
The 34-year-old owner was at the shop together with two men, one aged 36 and the other 23, who were installing security cameras.
Once handed the cash, the thief fled from the spot, the police said.
An inquiry is being held.