Ironically, it was the activity of two of his top deputies that ended his career. On Thursday, Letten announced his resignation after the actions of former first assistant US Attorney Jan Mann and assistant US Attorney Sal Perricone. Via the Washington Post:

Resignations of U.S. attorneys under a cloud of scandal are rare. In an unusual step, Deputy Attorney General James Cole traveled to New Orleans on Thursday and informed the district’s federal judges that the Justice Department had appointed a career prosecutor to investigate the allegations of misconduct in Letten’s office.

Letten’s resignation, effective Tuesday, comes eight months into a scandal that sparked the Justice Department investigation of his top deputy and a second veteran prosecutor in connection with anonymous online criticism of a man whose company is the target of a federal inquiry.

The two prosecutors, former first assistant U.S. attorney Jan Mann and former assistant U.S. attorney Sal Perricone, acknowledged using aliases to post comments on the Web site of the Times-Picayune newspaper. The comments were highly critical of Fred Heebe, the owner of a local landfill that was under federal investigation, according to court papers. Perricone, a member of Letten’s inner circle, resigned, and Mann was demoted.

The Justice Department’s Office of Professional Responsibility is investigating the episode, and last week a federal judge increased the pressure on Letten by calling for an independent counsel to probe the matter.

The judge, Kurt D. Engelhardt, also called for the department to investigate leaks of grand jury information to the media by prosecutors in the high-profile Danziger Bridge case, in which New Orleans police officers shot innocent city residents after Hurricane Katrina in 2005 and then tried to cover it up.

The New York Times has more:

Last month, the revelations of online misconduct reached Mr. Letten’s top assistant, Jan Mann. A federal judge, in a scathing 50-page order, broached the possibility of criminal conduct in regard to her online activities, as well as those of another senior prosecutor, Sal Perricone, who resigned in March.

The judge also revealed that another federal prosecutor had expressed suspicions about the comments to his supervisors in 2010.

The exposure of Ms. Mann, months after Mr. Letten’s avowals that Mr. Perricone had acted alone, raised doubts about the effectiveness of an internal investigation by the Justice Department. The revelations could also jeopardize hard-fought convictions — including those last year of police officers involved in post-Katrina killings on the Danziger Bridge — as well as continuing inquiries like a bribery investigation that appears to be steadily encircling C. Ray Nagin, the former mayor.

I really hope the Los Angeles District Attorney's office is paying attention. Given that it's under new management, it might be time to give serious attention to online commenting by assistants, anonymous or otherwise. It would appear some guidance on appropriate behavior is in order.

Here's a sample of what Mann and Perricone said about Mr. Heebe via anonymous comments. I snipped this from the the court pleading, which has plenty of other examples:

The text, for the visually impaired like me, reads as follows:

13. Many of Defendant's comments -- particularly those made under his most recent handle "Henry L. Mencken1951" -- involve Mr. Heebe, his family, and his company River Birch, Inc., as well as a federal investigation involving River Birch. In commenting on this ongoing investigation, Defendant made numerous statements about Mr. Heebe which Defendant knew to be false. The comments were part of an effort by Defendant to undermine Mr. Heebe's reputation in the community.

14. This conduct is particularly egregious given that Defendant was the senior prosecutor overseeing the ongoing investigation of River Birch at the time he posted the comments in question. Rather than maintain the degree of objectivity and professionalism expected of federal prosecutors, Defendant plainly prejudged Mr. Heebe's guilt prior to the conclusion of the investigation and then sought to use his insider knowledge in an effort to turn public opinion against Mr. Heebe.

I'm betting this isn't the only case like this. Just the first one.