http://abc7chicago.com/news/dallas-s...icers/1418642/

Defense officials confirm that Johnson had served as an Army Reservist until April of 2015.

Carlos Harris, who lives downtown, told the newspaper that the shooters "were strategic. It was tap, tap, pause. Tap, tap, pause," he said.

Brown said the suspects "triangulated" in the downtown area where the protesters were marching and had "some knowledge of the route" they would take.

Video posted on social media appeared to show a gunman at ground level exchanging fire with a police officer who was then felled.