A gunman attempted to rob a gas station early Sunday morning in Braintree, according to police. An employee at a Mobil on the Run gas station at the South Shore Plaza in Braintree told police a man wearing a hooded sweatshirt and a stocking cap partially covering his face entered the store shortly after 2 a.m., Braintree police said in a statement. The employee said the man brandished a handgun and demanded money, according to the statement. The employee refused to give him money, and the man fled the store.