The federal prosecutor who was leading the investigation into the still-unsolved murder of Washington, D.C., lawyer Robert Wone abruptly left his post last month, has hired a personal lawyer and will resign on Friday.

The reasons for the departure of Thomas “Tad” DiBiase, a deputy chief of the homicide division at the U.S. Attorney’s Office for the District of Columbia, are still unclear. The U.S. Attorney’s Office would not talk much about it, but there is plenty of speculation and contradictory accounts among police, prosecutors and defense attorneys — some of it circulating on the Internet.