Police in Dallas are on the hunt for a gunman who opened fire aboard a DART train Sunday, leaving one person dead and two others injured. The shooting took place around 4:30 p.m. following an argument between two passengers traveling on a northbound Green Line train near Hatcher Station, according to a DART spokesperson speaking to CNN. One of the people taking part in the dispute pulled a gun and fired. Two shooting victims were taken to a hospital, where one of them later died. Police said another bystander was treated at the scene for a shrapnel injury. The gunman...