Sanford police are investigating a robbery at the York County Credit Union. Police say a man entered the credit union on Main Street shortly before 2 p.m. Thursday and demanded money from a teller. He did not show a weapon, and fled on foot with an undisclosed amount of cash. Surveillance cameras showed the man wearing sunglasses, a black hat, and a brown hooded sweat shirt with a distinctive diamond pattern. He is described as heavy set, about six feet tall, in his early 20s with some facial hair. Police are asking for the public’s help in finding the thief.