By Cheney Orr and Brendan O’Brien GREENWOOD, Ind. (Reuters) -A 22-year-old bystander who witnessed a deadly shooting over the weekend at a shopping mall near Indianapolis was hailed as a hero on Monday for killing the gunman and limiting the number of casualties in the massacre. Local officials said the “Good Samaritan” – a man who was lawfully carrying a firearm – stopped the gunman almost as soon the suspect opened fire on Sunday in the food court of the Greenwood Park Mall in Greenwood, Indiana, outside of Indianapolis. In addition to the gunman, who had a rifle and several magazines of amm…