This is such a terrible problem, a maybe unsolvable problem, and I know more about it than I should, because of all the recent history reading of revolutions in Europe. Early on the "police," whatever was functioning in that capacity, WOULD shoot at the rock-throwing protestors, always cobblestones from that day to this in Europe, and we have never achieved their technology here until someone thought of frozen water bottles. And every time, unless the whole city was killed out (Lyon, 1793), the mob immediately attacked worse and more. The next day, the next week. Then there really WAS a revolution!! THAT is the problem: shooting them makes the rest mad, and there are so many of them, they cannot be stopped. In our case, antifa would stream in from other cities and light up Seattle.
There is one other problem, worse and more immediate: no one on earth can stop thousands of people running together. Maybe sometimes massed machine-gun fire can mow them down as they come, if you are lucky and well-placed and have enough machine guns (World War I in the trenches and WWII in the Pacific) but it often doesn't work anyway. And our police do NOT have machine guns. The police in their black riot gear and riot shields look SO SCARY, we think, why can't they turn the crowd? Maybe they could, the first time, with surprise --- after that, we're talking a war zone and maybe the now-armed rioters will just keep going and overrun all of them and kill every one of them. Our riot police know all this. This is why they don't shoot rioters. I am now reading the book 1848 when there were violent leftwing riots all over Europe and it was just one city after another overwhelming the riot police; they couldn't do anything with them.
Basically, when this happens, what you really have is a war, and Portland and Seattle won't face up to that. I mean, yeah, you can fight a war with these types but it IS a war and "police" just aren't in it. So I shouldn't have said they should shoot rioters; that was way too simplified and doesn't work.