What's most upsetting about this to me is listening to the people interviewed on NPR this morning who said that they felt some degree of solidarity with the police in the Dallas march, that the police where giving them an opportunity to protest peacefully, and a lot of progress had been made in Dallas since people fired on the police station last year.
One of the organizers of the march (A pastor, the guy who had a black cross with him but I didn't catch his name) said that at the time shots were being fired, he was standing with one of the Police corporals or heads of the police talking with him, and then shots rang out, the Pastor -- very emotionally -- said "My cross became a Sheppard's staff to lead people away from the gunfire as the officer [he was talking] to ran towards the gun shots."
This was on NPR's Morning Edition today. They'll probably replay it because it was a powerful interview.