A Salinas man accused of killing his girlfriend over the weekend pleaded not guilty in court yesterday. 22-year-old Byron Sumagang allegedly strangled 20-year-old Carole Sangco inside a car parked on Old Stage Road Sunday morning. Sangco was found unconscious and taken to the hospital where she was pronounced dead. Sumagang was treated for cuts on his wrists. The suspect claims they were both attempting to commit suicide. Sumagang remains in county jail in lieu of $1 million bail.