NEW TOWN, N.D. (November 19, 2012)--Authorities are investigating the shooting deaths of a woman and three of her grandchildren and the suicide of a man on a North Dakota Indian reservation.

Mountrail County Sheriff Ken Halvorson said Monday that the man who stabbed himself to death Sunday in Parshall is from nearby New Town and is a "person of interest" in the killings in New Town hours earlier of Martha Johnson, 64, and her grandchildren.

Both communities are on the Fort Berthold Indian Reservation, but Johnson and her grandchildren are not members of the Three Affiliated Tribes.

Halvorson said the children who were killed were Benjamin Schuster, 13, Julia Schuster, 10, and Luke Schuster, 6.

He said the children's 12-year-old brother who also was in the home called 911.