CHICAGO – An argument outside a Chicago hospital turned deadly when a man pulled out a gun and killed an emergency room doctor whom he knew, then ran into the hospital and fatally shot a pharmacy resident and a police officer, authorities said. The attacker, Juan Lopez, also died Monday but it was not clear if he took his own life or was killed by police at Mercy Hospital on the city's South Side, Chicago Police Superintendent Eddie Johnson said. Chicago "lost a doctor, pharmaceutical assistant and a police officer, all going about their day, all doing what they loved," Mayor Rahm Emanuel said, fighting back tears.