Bannerdrop on top of the occupied building. (picture from NYT). See a video of cops pepper spraying and beating students here and see a news video on the event here at NY1.
Read first-hand accounts of the re-occupation by the occupiers themselves and their reply to the university president at http://reoccupied.wordpress.com.
From the rooftop, the occupiers read the Situationist manifesto, “On the Poverty of Student Life.”