I read that the dumpster was being paid for by the two shirtless guys and was for their use. The neighbor kept putting his stuff in there forcing the dumpster to be emptied more often, incurring additional cost to the people paying for the dumpster and that it was always full of the neighbors stuff and they couldn't use the dumpster they were paying for.
Now, I know that dumpsters on construction sites get the same thing and I've seen some pretty heated stuff go on between job sites and such because of this. I had one project that was in the ghetto that the owner hired armed security for just that reason since the neighbors in the area were having a free for all with their dumpster. So I can kind of get it.
My opinion is that all three of these people were idiots. All three could have deescalated the situation without the taking of lives. Even though they will likely walk they'll end up spending money to lawyer up.