NEW TOWN, N.D. - Authorities have released the names of a grandmother and her three grandchildren who were shot and killed here Sunday.

Martha Johnson, 64, and three of her grandchildren - Benjamin Schuster, 13, Julia Schuster, 10 and Luke Schuster, 6 - were gunned down in her New Town home Sunday afternoon while Johnson's husband was out hunting, Mountrail County Sheriff Ken Halvorson told the Associated Press. The children's 12-year-old brother, who was also in the home but wasn't hurt, called 911, he said.

Hours later in Parshall, a community about 20 miles from New Town that is also on the Fort Berthold Indian Reservation, a New Town man in his 20s killed himself with a knife, Halvorson said.

He was being questioned by investigators about the New Town shooting when he committed suicide.

Neither he nor the FBI had released the man's name.

"It happened in front of a deputy and a highway patrolman," Halvorson said of the suicide.

The FBI, aided by the state Bureau of Criminal Investigation and the Bureau of Indian Affairs, is leading the investigation into five deaths with Mountrail County Sheriff Ken Halvorson, said an FBI spokesman.

A woman and three children were found Sunday afternoon, victims of "violent deaths," said Kyle Loven, spokesman in the FBI's regional headquarters in Minneapolis that includes North Dakota.

"We are looking at those deaths as homicides," Loven said today.

The FBI has taken the lead largely because New Town and Parshall are on an Indian reservation, Loven said.

"Right now we are the lead agency, working in concert with the BCI and the BIA," Loven said. "It really is a joint investigation."

Any serious crime on an Indian reservation typically can involve the FBI's jurisdiction, he said.

"We are confident there is no threat to the public at large," Loven said.

But the FBI's involvement does not mean necessarily that tribal members are involved in the case, Loven said.

New Town is about 60 miles southwest of Minot near the heart of North Dakota's Bakken oil boom. It also is the headquarters of the Fort Berthold Reservation of the Three Affiliated Tribes, the Mandan, Hidatsa and Arikara.

The FBI has agents stationed in Bismarck and Minot and its agents are on the ground today in New Town and Parshall, Loven said.

A new release from the Mountrail County Sheriff's Department said a boy called the Mountrail Co 911 center in Stanley at 3:17 pm saying someone had just came in and shot his family, but before the dispatcher was able

to gather any more information from the caller, he hung up the phone.

The shooting deaths of the woman and children were "very terrifying" and sad, not only for the family but the whole community, said the Rev. Grant Patterson, pastor of Bethel Lutheran Church in New Town. He knows the victims, he said.

Marc Bluestone, superintendent of the public school in New Town, said he decided to call off classes for today because of "the tragedy in our community."

Although he has not been told anything by the sheriff, from what he's heard from neighbors and friends, the child victims were students in the school.

"In the best interests of our community and school, with the limited information we have, my decision is to call off school for (today)," he said.