It's from Sylvia Matthews Burwell, head of the Office of Management and Budget:

And with that, the government is officially shutdown. Here's Wonkblog's guide to how the shutdown will work. Here's our interview with Alice Rivlin, who was head of the OMB last time there was a shutdown. "I remember we said let’s make sure we keep a record of exactly what we did for the next time it happens," she told us.