Micah Xavier Johnson, of Mesquite, is one of four people police said were responsible for ambushing police officers at a peaceful protest against nation-wide officer-involved shootings in Dallas Thursday. Police said officers cornered Johnson and negotiated with him for hours before talks broke down. Dallas Police Chief David Brown said Johnson told officers he was upset about recent shootings involving police and "wanted to kill white people. Especially white officers." After an exchange of gunfire, Brown said officers attached an explosive device to a bomb robot and detonated it near Johnson, killing him. A black SUV found at the scene...