NBCNews.comWhy are so many migrants crossing the US border? It often starts with an escape from violence in Central AmericaNBCNews.comAUSTIN, Texas — Patricia de Jesús Flores waited at a homeless shelter on the Mexican side of the U.S. border this week with her 7-year-old son, who she says witnessed a murder on a rooftop — one reason they left their home in Honduras.Why do some families risk crossing the US border?