Police do use teargas and mace for no reason. There are dozens (hundreds?) of videos of exactly that from the last week, including an aerial shot of Seattle PD instigating with mace at point blank range on protesters who were behind a barricade.
* https://www.facebook.com/omarisal/videos/10220021035848747/ - Livestream of 30+ minutes leading up to the incident. The interesting stuff starts at 26' in, but he gives a lot of good context on the protest leading up to then. The livestreamer was at the front line when they started pepper spraying, and in fact you can even see him in the aerial footage as he's next to a pink umbrella that makes a good landmark. It's very clear from ground eye view the violence was deliberately premeditated and coordinated by SPD and not in response to any immediate threat. No orders to disperse, or do anything else for that matter, are given prior to pepper spray, teargas, and flashbangs.
* https://mobile.twitter.com/izaacmellow/status/12676798206006... - Official SPD story claiming incident is a "riot" and was forced on them: " Crowd has thrown rocks, bottles and fireworks at officers and is attempting to breach barricades one block from the East Precinct."
I don't think you can watch these videos and come to the conclusion that at least in this instance, it's not the protesters rioting but rather the police. Then they're officially lying about it.
