SAN DIEGO (AP) — The acting chief of the Federal Emergency Management Agency left his job Monday after just six months, according to the Department of Homeland Security, the latest disruption in a year of mass staff departures, program cuts and policy upheaval at the agency charged with managing federal disaster response.

David Richardson is leaving the post after replacing previous acting head Cameron Hamilton. DHS did not comment on the reason for his departure.

“The Federal Emergency Management Agency and the Department of Homeland Security extend their sincere appreciation to the Senior Official Performing the Duties of the Administrator, David Richardson, for his dedicated service and wish him continued success in his return to the private sector,” a DHS spokesperson told The Associated Press.

A former Marine Corps officer who served in Iraq and Afghanistan and also led the DHS Countering Weapons of Mass Destruction office, Richardson had no previous emergency management experience when he assumed the role of “senior official performing the duties of administrator” in May.

Upon replacing Hamilton, who was fired one day after telling a House appropriations committee that he did not think FEMA should be eliminated, Richardson affirmed his commitment to President Donald Trump’s goal to push more disaster recovery responsibilities to the states and told FEMA employees he would “ run right over ” any staff who tried to obstruct that mission.

But Richardson’s effectiveness in leading the agency was questioned by members of Congress and FEMA staff.

When asked by a House committee why he did not arrive on the ground until one week after deadly July floods killed at least 136 people in central Texas, Richardson said he stayed in Washington, D.C. to “kick down the doors of bureaucracy,” but also said he was camping with his sons when the floods first hit over July 4 weekend and initially helped manage the response from inside his truck.

The Washington Post first reported the news about Richardson’s departure.