GRANGER -- Federal authorities arrested a man Monday after they said he threatened to stab staff members of U.S. Rep. Joe Donnelly.

Brett Keiling, 46, of 10130 Anderson Road, Granger, remains jailed on a criminal complaint accusing him of intimidating and interfering with Donnelly, of offering violence to a protected person, Donnelly, and of offering violence to another protected person, a member of Donnelly's staff, according to court documents in U.S. District Court in South Bend.

A member of Donnelly's staff took a call in the South Bend office at 9:30 a.m. Monday, according to an affidavit by Robert Dane, an FBI special agent based in South Bend.

"The caller, who identified himself as Brett Keiling, accused everyone in Donnelly's office of 'back stabbing him,'" Dane wrote. The employee wasn't sure what Keiling was talking about, but said he was upset.

She tried to talk with Keiling, but he said, "'I am going to come and back stab you, I mean literally come down and stab you,'" at which point the woman hung up, according to Dane.

The threats came 16 days after a gunman opened fire in Tucson, Ariz., at a public event featuring a member of congress. That shooting wounded 12, including the congresswoman, and killed six.

Keiling called Donnelly's office three more times Monday but made no more threats, according to Dane.

Keiling calls the congressman's office daily, and "Brett Keiling is known to both local and federal law enforcement as a subject who frequently calls to discuss current events ... During these telephone calls, Keiling is routinely irrational, confrontational, and uses vulgar language," Dane wrote, noting that he's spoken with Keiling numerous times.

Keiling has also called The Elkhart Truth repeatedly to complain that the FBI, Secret Service, Israeli Mossad and other groups are after him.

Keiling appeared Tuesday before a magistrate and has a detention hearing scheduled for next week in U.S. District Court.