WASHINGTON (ABC News) — Acting FEMA Administrator David Richardson resigned on Monday, according to multiple sources familiar with the situation.

Richardson, who was temporarily installed after the former Acting Administrator Cam Hamilton was essentially fired by Secretary of Homeland Security Kristi Noem.

Richardson was also in charge of the Department's countering Weapons of Mass Destruction office, and it is unclear if he will still stay on as the head of CWMD.

It is unclear who will lead the disaster management agency.