WASHINGTON: Dallas police ended a standoff with a gunman Friday morning by remotely detonating a "bomb robot," an unprecedented tactic by officers that rekindles concerns about the militarization of local law enforcement in the United States. The bomb blast killed a black US Army reservist identified by authorities as Micah Xavier Johnson , who shot dead five police officers and wounded seven others in Dallas on Thursday night following a peaceful protest over police shootingsof of black men. Technology warfare experts said the use of a robot to kill someone had major technological and legal implications for 21st century policing. "It's a first by police," said Peter Singer, author of "Wired for War," a book on the use of robots in conflict zones. Singer said that he knew of examples of the U.S. military in Iraq "jury rigging a surveillance bot to take out an insurgent down an alley." U.S. law enforcement has used remotely controlled devices before to help stop a suspect but not to kill anyone, law enforcement experts said.