The head of U.S. Citizenship and Immigration Services is stepping down from his post next month per the request of President Trump, according to a new report.

Lee Francis Cissna notified staff Friday that he would be leaving the Department of Homeland Security on June 1. It’s unclear what his plans are after departing the administration.

“During the past 20 months, every day, I have passionately worked to carry out USCIS’ mission to faithfully administer the nation’s lawful immigration system,” Cissna wrote to staff, according to an email obtained by the Associated Press.

Cissna’s job was in jeopardy last month as the agency coped with a surge of migrants crossing the border and a new caravan assembling. But Republicans including Sen. Chuck Grassley of Iowa went to bat for Cissna, and he did not leave with former Secretary of Homeland Security Kirstjen Nielsen.

Cissna’s position requires Senate confirmation. It’s unknown who will replace Cissna, although the Trump administration announced that former Virginia Attorney General Ken Cuccinelli would join the agency.