A 16-year-old boy who killed nine people and then himself on a Minnesota Indian reservation was wearing a bullet-proof vest when he chased a teacher and fellow students into a classroom and gunned them down.
Monday's rampage by Jeff Weise - the worst US school shooting since the 15-death Columbine massacre in 1999 - appeared to have been planned, investigators said. The spree left seven wounded, five of whom were still being treated in hospitals.
FBI agent Michael Tabman refused to speculate on a motive. He said he had no information on a report the high school student had revealed neo-Nazi sentiments in Internet postings.
Weise, who earlier reports mistakenly said was 17, identified himself as an "angel of death" and a "Native Nazi."
Other reports described Weise as someone who was often teased at school.
Tabman said there "could be some clues" in Internet postings or on the boy's computer which was seized but that and other matters were still under investigation.
Officials sealed off the remote town of Red Lake, 60 miles south of the Canadian border, while they investigated the bloodbath.
"Our community is devastated by this event," said Floyd Jourdain Jr., chairman of the Red Lake Chippewa Indian council. He called the tragedy "the darkest day in the history of our tribe."
Mr Tabman said Weise first went to the home of his grandfather Daryl Lussier, a sergeant with the Red Lake police department, where he shot him and a woman who was his companion.
He then stole his grandfather's bullet-proof vest and drove to Red Lake High School where he overpowered, shot and killed an unarmed security guard, 28-year-old Derrick Brun, at an entrance equipped with a metal detector, Mr Tabman added.
Walking down a hallway, Weise "saw a teacher and some students," fired at them and chased them into a room where he killed the 52-year-old teacher, Neva Rogers, and five students, and wounded the others, Tabman said.
At that point four policemen entered the school and exchanged fire with him. He then returned to the classroom and shot himself in the head, Tabman said.
"The nature of the activity would indicate there was some planning," he said, adding it appeared Weise acted alone and there was no sign he had a "hit list" of intended victims.
Witnesses said he was armed with a shotgun or rifle and at least one handgun.
US President George W. Bush was briefed on the shooting, White House spokesman Scott McClellan said, adding: "Our thoughts and prayers are with the families of those who were killed; this is a terrible tragedy."
It was the latest multiple shooting in a month of deadly gun violence in the United States, including the deaths of seven congregants at a church service near Milwaukee and four people in an Atlanta courtroom escape.