WASHINGTON (AP) — The Justice Department’s internal watchdog is investigating the top federal prosecutor in Massachusetts, prompted by U.S. Attorney Rachel Rollins’ appearance at a political fundraiser featuring first lady Jill Biden. That’s according to two people briefed on the investigation who weren’t authorized to publicly discuss the ongoing investigation and spoke to The Associated Press on condition of anonymity. The nation’s 93 U.S. attorneys are political appointees who are some of the highest-ranking federal law enforcement officials. Such an investigation targeting one of them is highly unusual. And the ethics concerns surrounding Rollins threaten to undermine Attorney General Merrick Garland’s efforts to restore the Justice Department’s reputation for political independence.