DALLAS, July 8, 2016 (Xinhua) -- Dallas police chief David O. Brown (C) speaks during a news conference following the sniper shooting in Dallas, the United States, July 7, 2016. Four police officers were killed and seven others injured as two snipers opened fire in downtown Dallas during a protest against officer-involved shootings across the United States on Thursday night. (Xinhua/Xu Xun)
