A high-school pupil went on a shooting rampage on an Indian reservation on Monday, killing his grandparents at their home and then seven people at his school, grinning and waving as he fired, witnesses said.
Armed with two handguns and a shotgun he then killed himself after exchanging gunfire with police.
It was the United States' worst school shooting since the 1999 Columbine school massacre in Littleton, Colorado, which left 15 people dead.
The teenage gunman rammed a pick-up truck into the wall of his school in Red Lake, northern Minnesota, before blasting his way through the metal detector and killing a security guard at the entrance.
He then walked down the hallway shooting and into a classroom where he opened fire, shooting dead a teacher and four pupils.
Sondra Hegstrom, 17, said a classmate pleaded: "No, Jeff, quit, quit. Leave me alone. What are you doing?"
The killer was identified as Jeff Weise, a 17-year-old pupil. Before the shootings at Red Lake high school, the teenager's grandfather and his wife were shot in their home and died later.
Weise had been suspended from school for some violation of the school rules and was receiving tutoring at home, said Kathryn Beaulieu, a member of the school board.
There was no immediate indication of Weise's motive, but pupils said he held anti-social beliefs, and had posted messages on a neo-Nazi website expressing admiration for Adolf Hitler.
A writer who identified himself as Jeff Weise of the Red Lake Reservation posted the messages under the nickname "Todesengel" - German for "angel of death".
An April 2004 posting by him referred to being accused of "a threat on the school I attend," though the writer later said he was cleared.
Like the Columbine killers Eric Harris and Dylan Klebold, Weise was obsessed with Goth culture, usually wore black and was a loner who was teased by other pupils.
Relatives told the St Paul Pioneer, a Minnesota newspaper, that his father had committed suicide four years ago, and his mother was living in a Minneapolis nursing home because she had suffered brain injuries in a car accident.
The death toll at the 300-student school included five pupils and Neva Rogers, 62, who had taught there for five or six years.
At least 14 other pupils were injured.
Ms Hegstrom described the killer grinning and waving at a pupil his gun was pointed at, then swivelling to shoot someone else. "I looked him in the eye and ran in the room, and that's when I hid," she told The Pioneer.
The rampage in Red Lake, one of America's most deprived areas, was the second fatal school shooting in Minnesota in 18 months.
Two students were killed at Rocori high school in Cold Spring in September 2003.
Student John Jason McLaughlin, who was 15 at the time, awaits trial in the case.