By Michael Noble Jr. TULSA, Oklahoma (Reuters) -A man armed with a rifle and a handgun killed four people inside a medical building in Tulsa, Oklahoma on Wednesday before fatally shooting himself, police said, in the latest of a series of mass shootings to rattle the United States. Eyewitness video of first responders arriving at the St. Francis Hospital campus showed a police officer immediately pulling a high powered rifle from the boot of his car. Armed police then ran towards the medical center. Police arrived at the medical center three minutes after receiving a call about the shooting on…