Secretary of Homeland Security Janet Napolitano announced on Friday that she was leaving her government post to run the University of California system.
A former Governor of Arizona, Napolitano was one of the few first-term Cabinet officials to stay in their post.
She had given no indication prior to today's announcement that she was considering leaving the job.
The move will now leave both DHS and Immigration and Customs Enforcement without leadership, as ICE Director John Morton resigned in June. The two most important bodies related to immigration are headless at a time of a national conversation about the overhaul of the immigration system.
Of the top 44 positions within DHS, 10 are acting, two are vacant, two are about to be vacant, and one, Customs and Border Protection Commissioner, doesn't exist anymore.
Reaction to the news of Napolitano's departure was mixed. Sen. John McCain (R-Ariz.) said the people of Arizona should be proud of the former governor's service.
"We have had our share of disagreements during her time as Secretary, but I have never doubted her integrity, work ethic or commitment to our nation’s security," McCain said in a statement.
But one immigrant rights group had a different take. Chris Newman of the National Day Laborer Organizing Network said Napolitano's "tenure on immigration — perhaps with the sole exception of DACA — has been an unmitigated failure. ... She ultimately will be remembered as the Secretary who brought Arizona's repugnant policies to the rest of the country."
Under the Obama administration, deportation numbers have risen every year, which has upset immigrant rights and Latino groups. The United States deported a record 409,849 immigrants in fiscal year 2012, up from 396,906 last year.
Napolitano was the third Secretary of the Department of Homeland Security, which was created after Sept. 11, 2001, and the first who hailed from a border state.
Updated 7/12/2013 at 11:24 a.m. Tracy Greer, Jude Joffe-Block and Michel Marizco contributed to this report.