The first identified police officer, Brent Thompson, was a US Marine who fought in Iraq and Afghanistan... He was a newly married grandfather, a former U.S. Marine and a veteran cop who had gone to Iraq and Afghanistan to help train local police. But Brent Thompson died protecting the rights of fellow Americans to criticize his brethren in blue. The 43-year-old Thompson, who joined the Dallas Area Rapid Transit police department in 2009, was the first identified of the five city police killed in a coordinated sniper attack...