DALLAS, July 10, 2016 (Xinhua) -- A woman mourns for killed police officers outside Dallas police headquarters in Dallas, the United States, on July 9, 2016. Five police officers were killed and seven others wounded Thursday by a black gunman who ambushed the police during a black protest in Dallas, Texas to retaliate against white policemen in the wake of the Louisiana killing. This is the deadliest police-killing incident since the Sept. 11, 2001 terror attack. (Xinhua/Zhang Yongxing)
