PIERRE (AP) - Federal authorities have charged a man in the stabbing of the Bureau of Indian Affairs superintendent on the Crow Creek Indian Reservation in South Dakota.

Authorities allege that Brian Iron Boulder, 51, stabbed Patrick F. Duffy in the back with a knife on March 25, penetrating Duffy's chest wall. Duffy was in critical condition for a time but is recovering.

Court documents don't indicate a motive for the alleged stabbing. BIA special Agent Tino Lopez said in an affidavit that a witness told him Iron Boulder often talked with Duffy at his office, and that the stabbing occurred after one of the conversations. Lopez said Iron Boulder admitted to him that he stabbed Duffy.

Duffy's public defender, Douglas A. Abraham, declined comment to The Associated Press on Tuesday.

Documents show that Iron Boulder on Friday waived his right to a detention hearing. He will remain in custody until a preliminary hearing that was not immediately scheduled. U.S. District Judge Roberto Lange on Monday did set a June 2 date for a jury trial on an assault charge that carries a maximum punishment of 20 years in prison.

Iron Boulder is a member of the Standing Rock Sioux Tribe but has been living on the Crow Creek Reservation, where Duffy oversees BIA facilities in Fort Thompson and manages tribal land, according to the Capital Journal.