On September 10th, 2001 FEMA was posed to have a major role in domestic terrorism, prevention and response. This upgrade in role had been underway since a WH [White House] press conference that occurred in early May in which then President Bush announced that VP Richard Cheney would lead a major study to determine how the Exective Branch was organized now and should be organized for dealing with terrorism.
Some of that history was documented as well as events and assignments in a rather unusual document assembled by virtue of reference to existing unclassified documents and this chron was updated to some extent between September 11th, 2001 to January 20, 2009.
The URL for the chronolgy is set forth below:
http://www.fas.org/irp/agency/dhs/fema/chron.pdf