From a January 26 Times-Picayune article:

The FBI, alleging a plot to wiretap Democratic Sen. Mary Landrieu's office in downtown New Orleans, arrested four people Monday, including James O'Keefe, a conservative filmmaker whose undercover videos at ACORN field offices severely damaged the advocacy group's credibility.

FBI Special Agent Steven Rayes alleges that O'Keefe aided and abetted two others, Joseph Basel and Robert Flanagan, who dressed up as employees of a telephone company and attempted to interfere with the office's telephone system.

A fourth person, Stan Dai, was accused of aiding and abetting Basel and Flanagan. All four were charged with entering fedral property under false pretenses with the intent of committing a felony.