An ABC News tipster describes the scene at 47 West 66th Street:

"Everyone is all hands on deck here. This place is working like a well oiled machine. Most of the regular weekday staff is here helping out the weekend staff with anything. The weekend staffers are a very strong team and have been amazing so far. Most of the 5th floor execs are in as well in the newsroom providing support."

Elizabeth Vargas will anchor this evening's World News Tonight. Diane Sawyer is also on standby. "Expect to see parts of the new set that have been constructed to be used tonight," the tipster added.

> Update: 4:42pm: A second tipster adds: "David Westin is the compasisonate, calm in the storm. an absolute rock, leading his troops through a most difficult day."