The sticker on this DC Police vehicle is for 'All Out DC', which is apparently affiliated with antifa:
"The Antifa groups are using the website defenddc.org to organize their comrades. Some of the Antifa groups listed are: Black Lives Matter DC, All Out DC, Autonomous Liberation Collective NYC…"
https://rairfoundation.com/action-alert-antifa-will-target-trump-supporters-on-12-12-at-the-marchfortrump-dc-rally-demand-police-protection/