The people killed by a gunman at a mall near Dallas over the weekend include two elementary school-age sisters, a couple and their 3-year-old son, a young engineer and a security guard. The victims represent a multicultural cross-section of the metropolitan area's increasingly diverse suburbs. Cox Elementary School students Daniela and Sofia Mendoza, grades four and two, were among those slain Saturday at Allen Premium Outlets, according to officials in the Wylie Independent School District. They were remembered as ''the kindest, most thoughtful students with smiles that could light up any room,'' Principal Krista Wilson said in a letter to...