Most of all, it was a tragedy. Five law enforcement officers lost their lives protecting the public. Their families and friends lost loved ones. The wounded and their families were also touched by tragedy. They deserve our gratitude and support.
The blame for this lies with one man. The marchers are not to blame. The gunman was not part of the march. The gunman had no known ties to "Black Lives Matter." Those who sympathize with that movement (among whom I count myself) are not to blame. Saying black lives matter TOO does not deny that white lives matter, blue lives matter, all lives matter. It's possible to both support the police and want to see justice on America's streets.
Texas Lt. Governor Dan Patrick's statement that the marchers were hypocrites for running from the gunfire was appalling. It's not hypocritical to want the police to protect you, not just when a gunman is shooting, but all the time.
Some on social media objected when they heard that the police were in "negotiations" with the trapped gunman. They cheered the police chief's decision to use a robot to detonate an explosive device near the barricaded gunman to kill him. (One person on social media colorfully expressed this by saying he'd have been willing to give the world's last unicorn a C4 enema and send him in to take out the gunman.) It's hard to second guess the police chief, but one reason to "negotiate" with a gunman and wait him out is to obtain additional information from him. It's not done out of any sympathy for his life. Kill him and you lose a chance to learn from him whether there might be conspirators on the loose who might pose an ongoing threat. The police chief's decision not to wait was based on his assessment of the immediate threat, which is as it should be. The social media sentiment was based on animus towards the gunman, which shouldn't be used to determine police tactics.
One of the marchers in Dallas was openly carrying an AR-15, which is his legal right. When the shooting began, he was identified by Dallas Police as a suspect. His brother advised him to hand his gun to a police officer so he wouldn't be mistaken for the shooter, which he did. (In Minnesota, just a day earlier, another man, legally licensed to carry a gun, was shot by police during a routine traffic stop after informing the officer that he was carrying a weapon.) The theory that "only a good guy with a gun can stop a bad guy with gun" seems to have a fatal flaw. If the gun you're carrying makes you a suspect in the eyes of police, if the gun you're carrying gets you shot, then maybe the theory that more guns on the street increases public safety needs rethinking.
According to the Chicago Tribune:
Richardson. Academy of Combative Warriors. Special tactics. "Shooting on the move." You'd think law enforcement might closely monitor students of such schools afterwards. Recent court rulings may give you a right to carry a gun. Law enforcement should have the right to know that you have a gun. And a right to know you are training to use your gun in military-style ways. You can't prevent all "lone wolf" mass murders, but why make it all but impossible to do anything until after the shooting begins? The Dallas gunman was probably within his legal rights to carry his long gun right up until the moment he first pulled the trigger.[The Dallas gunman] had practiced military-style drills in his yard and trained at a private self-defense school that teaches special tactics, including "shooting on the move," a maneuver in which an attacker fires and changes position before firing again. He received instruction at the Academy of Combative Warrior Arts in the Dallas suburb of Richardson about two years ago, said the school's founder and chief instructor.
Source: Chicago Tribune.
Last thought: I don't want to argue with you. I want to grieve.