WASHINGTON — The U.S. Attorney announced Monday that he will step down next month after more than five years in the position — the longest a chief federal prosecutor for D.C. has served in decades.

U.S. Attorney Ronald C. Machen, Jr., announced Monday that he will step down effective April 1 and return to private practice, The Washington Post reports.

By April, 45-year-old Machen will have served longer as U.S. attorney in the District than anyone since 1979, when Earl J. Silbert stepped down.

The Justice Department named Vincent H. Cohen, Machen’s top assistant, as acting U.S. Attorney, the Post reports.

“After more than five years as United States Attorney, it is time for me to step down,” Machen said in a statement released after he met with senior staff earlier Monday. “I am proud of the work we have done together to achieve justice in the courthouse and to build bonds of trust with the community that we serve.”