The U.S. Attorney for the District of Columbia will step down after five years on the job to return to private practice.

Ronald Machen (MAYCH-ehn) announced his resignation Monday. He says he will leave the position April 1. His top deputy, Vincent Cohen Jr., will become acting U.S. attorney.

Machen was appointed by President Barack Obama in 2010. In a statement, Attorney General Eric Holder pointed to Machen's success in prosecuting terrorism, public corruption and violent crime. Holder called Machen "a forceful champion of justice on behalf of the American people."

Machen leaves office amid an investigation of former District Mayor Vincent Gray and his 2010 campaign. A year ago, a prosecutor in Machen's office said in court that Gray knew about a scheme to illegally fund his campaign.