On July 7, 2016, Micah Xavier Johnson ambushed and shot twelve police officers and two civilians in Dallas, Texas, United States, killing five of the officers. The shooting occurred at the end of a protest against police killings in the aftermath of the shooting deaths of Alton Sterling in Louisiana and Philando Castile in Minnesota in the preceding days. Police used a robot to set off a bomb, killing Johnson and ending a standoff. Some experts believed it was the first time in U.S. history a robot was used by police to deliver lethal force. It was the deadliest incident for U.S. law enforcement since the 9/11 terrorist attacks.

• http://en.wikipedia.org/wiki/2016 shooting of Dallas police officers