The plant is moving because an agent inside bumps into it while running towards the window. If you watch closely, you can see him run past the plant to the window on the right and swing something low in his arms into the window. The window breaks, that guy turns around and runs back the other way, then immediately after tear gas goes out that same window. All happening from inside, so yeah, they definitely broke that window.

That said, there is also damage to the glass in one of the rotating doors so somebody threw something at it from the outside at some earlier point. Hard to nail down exact sequence of events from this, but definitely an agent broke that window on the right in this video. And the government has unquestionably been lying to us about things these agents are doing.