Examples:

https://twitter.com/hardpassbruh/status/1266990770436706304
https://twitter.com/IceIce718/status/1266948300420325377?s=19
https://twitter.com/frogindafog/status/1267678043742646272?s=09
https://twitter.com/cdelvallejr/status/1267665337023107073?s=19
https://twitter.com/Dick_Kannon/status/1267464772234199044?s=09
https://twitter.com/fleccas/status/1267326702771793920?s=09

Very convenient how they appeared overnight, with no construction site having been there the day prior.

Bonus:
https://twitter.com/loch_northern/status/1267634593579937793?s=09 Cops caught in the act unpacking bricks

bonus bonus:
https://twitter.com/loneangeI/status/1267681107216084993?s=19 Cops vandalizing cars
cops looting

It would be more an argument that some police are trying to make the situation worse and find excuses to stop both the riots and or peaceful protests. There have in the past been police officers joining in some protests out of uniform and then investigating violence to make protests look bad. Although at the same time there are activists who wish to accelerate issues and would go out and drop off bricks in some key locations for later use by rioters.

And both Cops and Activists push a lot of propoganda when it comes to these issies to make the other look worse.