Um...I'm sorry your son was acting erratically in public with a very obvious dangerous weapon and actions were taken so he didn't potentially hurt someone else? Was that better?
Fact is we don't know what prompted the shooting. Some eye-witnesses said he was acting erratically. So a couple cops come to the scene, kids is freaking out a bit, cops try to talk to him, maybe he is incoherent somewhat. The he turns and runs toward a busy store carrying a sword, and doesn't respond to officers requests to stop. What do you do? "Hey Bob, despite all our training, I bet he is just a misunderstood kid. Let's wait and see if he tries to slash up that Panda Express before we step in. We don't want this to be mis-construed." You do realize this is where some of this may be going at some point. The headline would then read "police watch as crazy man kills 4 and wounds a dozen more at a Panda Express, to make sure they are not taking unreasonable action because he was acting strangely. Citizens applaud the police for allowing the rampage rather than perhaps setting off a controversy about whether or not they should have dealt with a potential threat."