Officers Killed in Dallas Ambush

Micah Johnson, the suspect in the Dallas shooting, is seen in this undated Facebook post.

A clerk looks at broke windows shot out at a store in downtown Dallas, Friday, July 8, 2016.

Dallas police chief David Brown, left, and Dallas mayor Mike Rawlings, right, talk with the media during a news conference, July 8, 2016, in Dallas.

Police officers stand guard at a baracade following the sniper shooting in Dallas on July 7, 2016.

Dallas police stand watch near the scene where four Dallas police officers were shot and killed on July 7, 2016 in Dallas, Texas.

A Dallas police officer, who did not want to be identified, takes a moment as she guards an intersection in the early morning after a shooting in downtown Dallas on July 8, 2016.

A Dallas police officer covers his face as he stands with others outside the emergency room at Baylor University Medical Center, July 8, 2016.

Dallas Police Chief David Brown leaves the Baylor University Medical Center after a visit on July 8, 2016.

People rally in Dallas, Texas, on Thursday, July 7, 2016 to protest the deaths of Alton Sterling and Philando Castile.

People rally in Dallas, Texas, on Thursday, July 7, 2016 to protest the deaths of Alton Sterling and Philando Castile.

A man lays on the ground after yelling "Don't shoot me" at police during a rally in Dallas, Texas, on Thursday, July 7, 2016 to protest the deaths of Alton Sterling and Philando Castile.