A U.S. Army reservist who served in Afghanistan, embraced militant black nationalism and professed a desire to "kill white people" has been named by authorities as the lone gunman in a sniper attack on police in Dallas that left five officers dead.

 Dallas police were in a standoff with a suspect on Friday after snipers killed five officers and wounded six, one of the worst mass police shootings in U.S. history, during protests against the killing of two black men by police this week.