LODGE GRASS, Mont. (AP) — The man suspected of gunning down his elderly grandmother, cousin and cousin's boyfriend on Montana's Crow Reservation was described Wednesday as a regular churchgoer who was haunted by a traumatic event that he had witnessed as a teenager.

Police, game wardens and tribal authorities were combing county roads looking Sheldon Bernard Chase, 22, while schools on reservations in southeastern Montana and western North Dakota were closed and residents stayed indoors for safety.

The FBI said Chase is suspected of using a rifle Tuesday afternoon to kill his grandmother, Gloria Sarah Goes Ahead Cummins, 80; his cousin, 21-year-old Levon Driftwood; and her boyfriend, 20-year-old Rueben Jefferson.

The shootings happened at Cummins' home about 10 miles outside Lodge Grass, a town of 500 people near the Wyoming border. Chase lives with his uncle in a mobile home about 100 feet from the modest log house, said city clerk Cody Not Afraid.

On Wednesday, police tape stretched across Cummins' property and Bureau of Indian Affairs law enforcement officers kept onlookers from approaching.

It was unclear what led to the shootings or how Chase was identified as a suspect. Chase has a history of mental illness and is considered armed and extremely dangerous, said Eric Barnhart, FBI supervisor in Billings.

People in Lodge Grass described the victims and the suspect as coming from a prominent, well-respected family in the community. Chase moved there about a year ago from North Dakota, where he had grown up, and was attending Little Bighorn College about 20 miles away in Crow Agency, said Rev. Jim Antoine, the priest at Our Lady of Loretto Catholic Church.

Antoine said he baptized Chase as a child, and Chase and his two brothers frequently traveled with their mother from North Dakota to visit her family. Since moving to Lodge Grass, Chase went to Mass several times a week, sometimes with family members but often alone after his classes were done, Antoine said.

Antoine described Chase as a "beautiful and good person," but said Chase had witnessed a traumatic event when he was a teenager that affected him mentally and which he still carries around with him. Antoine declined to say what Chase had witnessed.

"I know Sheldon had problems dealing with this. It haunted him but he wouldn't talk about it. He was affected emotionally by that experience," Antoine said.

Despite that, Antoine said the shootings did not strike him as "normal behavior" for Chase and prayed for him to be found without harm coming to him.

Dennis Bravo, the maintenance man at the church, saw Chase at Mass two or three times a week, but said "there was something strange" about Chase.

"Looks like a nice kid from a distance, but when you see him face-to-face, well, my wife says he spooked her," Bravo said

Bravo described an incident after one Mass in which he said he saw an angry Chase yelling at a young child, possibly for riding a bicycle around the church.

Lodge Grass residents described Cummins as the matriarch of an extended clan on the reservation, a devout Catholic who was also very knowledgeable about Crow traditions.

"If someone wanted to know about the Crow way of life, we'd send them to her. She had a great knowledge about the Catholic way of life and the Crow way of life," Antoine said.

Crow took in Driftwood and Driftwood's sister as teenagers after their mother died, taking care of the girls until she had a stroke several years ago that made it difficult to get around, Antoine said. Then, the girls stayed on and took care of their grandmother, with Driftwood's boyfriend Jefferson living with them.

Driftwood and Jefferson have two children, ages 2 and 3, Antoine said.

Schools were closed on Wednesday, and some Lodge Grass residents said they were frightened to leave their homes as long as the suspect remains at large. "We'll run to the store and do what we have to do, but otherwise, we're going to stay home," Taiann Crooked Arm said on her way to buy groceries.

Schools were also closed in the Mandaree area on North Dakota's Fort Berthold Indian Reservation, where Chase has family. "It's precautionary," Three Affiliated Tribes spokeswoman Glenda Embry said. "There is a lot of police activity in the area. Tribal police are on alert."

Chase is described as 6 feet, 2 inches tall with brown hair and brown eyes and weighing 230 pounds. The FBI said he is believed to be driving a white Toyota Corolla with North Dakota plates.

Anyone who sees Chase was asked not to approach him but instead call law enforcement. Meanwhile, authorities throughout the state, as well as in Wyoming, North Dakota and South Dakota have been notified of the manhunt.

Crow tribal secretary Scott Russell warned against speculation on what sparked the shooting until all the facts are known. He said he could not recall a tragedy of such magnitude among the close-knit tribe.

"This is pretty devastating to the community and the Crow Nation," he said. "We are all in shock."