Bucks County authorities are looking for a man who robbed a Burger King on Street Road in Warminster late Saturday night. It happened around 11:30, a half-hour after the dining room closed.  Police say he got in through the drive-up window, which is open until 2:00am.  Employees told police he pulled a small handgun and forced them into an office, and then escaped with an undisclosed amount of cash.