The only mention I read that sounded like a tank used the words "wheeled tank". That could easily be a Stryker or LAV-25. If so that's more of an APC than an actual tank. Its not like someone drove an M-1 Abrams to the Whitehouse. That would be a big deal.

Hypothetically if the Marines do act in some way you will likely see a shit-ton of LAV-25 in DC. The Marines have hundreds of them. They're fast(60 mph), they can wade across rivers so blocking bridges is useless and they have a 25mm main gun which will blow the shit out of anything other than a MBT like an M-1. They also don't weigh a lot so they won't tear up roads etc. Shit like armored SUVs/limos, or bearcats won't last 2 minutes against 25mm AP rounds. Cut right through that like its nothing.

https://en.wikipedia.org/wiki/LAV-25

Anyway... seeing 1-2 of this type of vehicle isn't that surprising to be honest. The SS or Marines that defend the WH might have one nearby. Now if you see like 20+ of them then some serious shits going on. Like military coupe serious.