By Lori Grannis
MISSOULA, Mont (Reuters) - Federal agents and police fanned out across four Western states on Wednesday in search of the gunman who shot and killed a young woman, her boyfriend and her grandmother on the Crow Indian Reservation in Montana.
The suspect, Sheldon Bernard Chase, 22, was considered "armed and extremely dangerous" by authorities looking for him in Montana, Wyoming, North Dakota and South Dakota, FBI and tribal officials said.
The shootings occurred on Tuesday near the town of Lodge Grass, a rural community of roughly 500 people about 60 miles southeast of Montana's largest city, Billings, and 20 miles north of the Wyoming border.
The Little Bighorn Battlefield National Monument, where Lieutenant Colonel George Armstrong Custer and his cavalry unit died fighting Indian forces in 1876, lies several miles to the north of Lodge Grass on the reservation.
Details of the shooting remained vague a day after the violence erupted.
Tribal officials said all three victims were tribal members, identified by the FBI as Gloria Sarah Goes Ahead Cummins, 80, her granddaughter Levon Driftwood, 21, and Driftwood's boyfriend, Rueben Jefferson, 20. Driftwood was believed to be Chase's cousin.
FBI spokeswoman Debbie Bertram said the three were all shot with a high-powered rifle.
Chase, who was not enrolled as a current member of the Crow Agency reservation, is a member of the Crow tribe, a tribal spokeswoman confirmed.
Crow Tribal Chairman Black Eagle said in a statement that the tribe remains in a state of shock.
"At this point, we don't know the details," he said, adding that the Crow Nation was deeply affected by the loss of fellow tribe members.
"(We) are asking for prayer from all denominations for the families and all others affected by this sudden and tragic incident," he said.
Authorities said the shooting occurred at a house on a remote corner of the sprawling reservation about 10 miles southwest of Lodge Grass.
The FBI described Chase as standing over 6 feet tall and weighing 230 pounds. They said he may be driving a white Toyota Corolla with North Dakota license plates.
(Writing by Steve Gorman; Editing by Cynthia Johnston)