A close-knit community on the Tulalip Indian Reservation has struggled to find answers following the shooting at a high school on Washington's Puget Sound in which a young gunman from a prominent family opened fire, killing one person and injuring four others -- including two of his cousins.

"What triggered him? That's what we need to find out," asked state Sen. John McCoy, a tribal member. "Because from all we have determined, he was a happy-go-lucky, normal kid."

The shooter, who also died in the attack, was Jaylen Fryberg, a popular freshman at Marysville-Pilchuck High School, a government official with direct knowledge of the shooting told The Associated Press. The official spoke on condition of anonymity because he was not authorized to speak to the media.

As the community coped and the investigation continued, a newly hired teacher was being hailed as a hero for confronting the gunman in the busy school cafeteria.

First-year social studies teacher Megan Silberberger intervened in the attack in Marysville, 30 miles north of Seattle, teachers union president Randy Davis said.

The teacher intercepted the gunman as he paused, possibly to reload, student Erick Cervantes told KIRO-TV.

"I'm completely amazed by her actions, and I feel for her," Davis told The Associated Press. "I don't know why she was in the cafeteria, but I'm just grateful she was there."

A school resource officer also ran to the scene, Davis said.

Davis said he had spoken briefly with Silberberger, who was traumatized. The Marysville School District released a statement in which the teacher thanked people for support and asked for privacy.

Of the four surviving students, Nate Hatch, 14, remained in serious condition and was improving Sunday in intensive care at Harborview Medical Center in Seattle. Andrew Fryberg, 15, remained in critical condition in intensive care, the hospital said. Both are cousins of Jaylen Fryberg.

Shaylee Chuckulnaskit and Gia Soriano, both 14, remained in critical condition Sunday at Providence Regional Medical Center Everett. Both were in intensive care, the hospital said.

All four have head wounds.

Soriano's family released a statement, saying they appreciated "your thoughts and prayers. Our hearts go out to the other victims and their families."

The girl who died in the shooting has not been officially identified.

It wasn't clear if the shooter committed suicide or if he accidentally shot himself in the struggle with the teacher.

A .40-caliber handgun was recovered at the scene, authorities said.

Fryberg left months of troubling messages on social media, and friends said he'd recently been in a fight over a girl. One of his tweets said, "It breaks me ... It actually does ..."

Students and parents said Fryberg played football for the high school and was freshman prince in the 2014 Homecoming court.

Lucas Thorington, 14, had known the victims and the shooter since middle school.

"He had a good life. He was very well known," Thorington said Saturday. "I don't know what happened."

Marysville-Pilchuck High School has a number of students from the nearby reservation.

Tribal chairman Herman Williams Sr. said his community was reeling.

"These are our children. They are suffering, and their lives will be forever changed," he said.

Ray Sheldon, 82, said Tulalip and Marysville are relatively integrated, though he remembers being the only Native American in his class when he went to school.

"Time moves along and we move with it," Sheldon said.

On the reservation, everyone "is related in one shape or form," McCoy said Saturday. The shooter's grandmother was his secretary for about 15 years.

"The family, both sides, are very religious," he said. "If I were to walk into their homes right now, they would probably be praying."