Tulsa (United States) (AFP) – The gunman who shot dead four people at a hospital in the US state of Oklahoma killed the surgeon whom he blamed for pain after back surgery, police said Thursday. The suspect, identified as Michael Louis, stormed into the Saint Francis hospital in the city of Tulsa on Wednesday with a rifle and a handgun, in the latest mass shooting in the United States in recent weeks. Louis had recently been operated on by surgeon Preston Phillips at the hospital and had called the clinic to complain of continuing back pain, Tulsa Police Chief Wendell Franklin said during a pre…