A Silver Alert has been issued for Pima county sheriffs department. This is the Arizona Department of Public Safety. Pima county Sheriff's Department is looking for white male, Robert Gaston, five foot seven inches, 150 pounds, gray hair, brown eyes, wearing a brown shirt and black sweat pants. last seen driving a 2003 gray dodge Dakota pickup, Arizona license number 4 5 7 h p m. in the area of 1600 block of South Whetstone Avenue in Benson, Arizona.