Scott police tonight arrested a Mt. Lebanon man after they said he used a BB gun to threaten workers at the Sunrise Senior Living Center on Greentree Road. Police said Stanley Rokosz, 87, of 814 Country Club Drive, went to the center shortly after 4:30 p.m. demanding that he be allowed to take his wife, who is living at the center, back home. Center employees told police Mr. Rokosz waved the gun and told them to lie on the floor. Police said the workers, who had had confrontations with Mr. Rokosz several times over the past two years, called police. When they arrived, the found Mr. Rokosz sitting in his car in the center parking lot. Police responding from Scott, Green Tree and Heidelberg could see the gun on the seat beside him and were not initially certain it was a BB gun. They arrested him without incident. Mr. Rokosz was being held on charges of aggravated assault, terroristic threats and disorderly conduct.