At least three people were killed and multiple others were wounded during a mass shooting Wednesday at a medical building in Tulsa, Oklahoma, police said. The gunman was also dead, authorities said. It was not clear if he died from a self-inflicted gunshot or was killed by police. Police described a “catastrophic” scene at the Natalie Medical Building, about six miles south of downtown Tulsa. The building had hundreds of people inside when the gunman opened fire, cops said, adding they could not provide a definitive number of injured victims. The building was locked down as officers went floor…