SOUTH BEND — The Granger man charged with threatening an aide to then-U.S. Congressman Joe Donnelly in 2011 pleaeded guilty Friday in District Court.

Brett Keiling, 48, pled guilty before District Judge Robert Miller Jr. to the felony offense of threatening to assault an employee of the United States with the intent to interfere with the performance of official duties.

Keiling was originally arrested in January 2011 after he threatened to stab members of Donnelly’s staff during a phone call to Donnelly’s South Bend office.

“The caller, who identified himself as Brett Keiling, accused everyone in Donnelly’s office of ‘back stabbing him,’” FBI special agent Robert Dane wrote at the time in an affidavit. Dane noted that Keiling then told the staffer, “I am going to come and back stab you, I mean literally come down and stab you.”

In June 2011, Keiling was ruled unfit for trial.

The case is being prosecuted by Assistant United States Attorney Barbara Brook.

Keiling’s sentencing is scheduled for April 15.