A US teenager has shot dead nine people - seven of them in a rampage through a school that ended when he apparently killed himself.
He earlier shot his grandfather and his grandfather's partner, police said.
At least 12 other people were hurt at Red Lake High School on a Native American reservation in the northern state of Minnesota.
It was the deadliest school shooting since the Columbine killings in 1999 when two teenage gunmen killed 13.
North Country Regional Hospital in Bemidji received six casualties, one of whom died.
Two of them were later transferred to another hospital in Fargo, North Dakota, where they remained in critical condition with head wounds.
Officials at North Country said all the injuries they had dealt with had been gunshot wounds - to the head, face, hip or chest.
Some of the victims were shot at close range.
"It looks like they were shooting at people's heads," one of the doctors who dealt with the injured told reporters.
"The shooter was intent on something... I think there was an intent to kill."
All those sent to North Country were male and under the age of 18, but they have not been identified.
The three people still being treated there were in non-critical condition.
Monday's carnage began when the boy, identified by school officials as 17-year-old Jeff Weise, shot dead grandfather Daryl Lussier - a veteran police officer - and his partner.
They died at their home in the Red Lake reservation, about 240 miles (390km) north of the state capital, St Paul.
US SCHOOL SHOOTINGS
April 2003: Teenager shoots dead headteacher, then kills himself, at Pennsylvania school
April 1999: Two teenagers shoot dead 12 pupils and a teacher, then kill themselves at Columbine School, Colorado
May 1998: Fifteen-year-old shoots dead two pupils in a school cafeteria in Oregon
March 1998: Two boys, aged 11 and 13, kill four girls and a teacher in Arkansas
October 1997: Teenager stabs mother, then shoots dead two pupils at a school in Mississippi
Armed with at least two weapons - a handgun and a shotgun thought to have been taken from his grandfather - the youth then drove his grandfather's police car to the school, reports said.
The shooting there is said to have occurred shortly before 1500 (2100 GMT) on Monday.
The student shot dead a male security officer at the door and walked down the hallway to a classroom, where he fired at pupils, killing five of them and a female teacher.
One survivor, Red Lake pupil Sondra Hegstrom, told the Pioneer of Bemidji newspaper: "You could hear a girl saying, 'No, Jeff. Quit! Quit! Leave me alone. Why are you doing this?'
"Boom, boom, boom, and then no more screaming."
Other witnesses said the teenage gunman was "grinning and waving" as he fired. Pupils and teachers dived for cover and used mobile phones to call police.
When the police arrived, a gun battle with the boy ensued before he retreated to a classroom where he is believed to have shot himself, FBI spokesman Paul McCabe said.
Red Lake tribe chairman Floyd Jourdain said: "This is, without doubt, the darkest hour in the history of our tribe.
"It's extremely painful. The community is in utter shock. Our hearts go out to the families."
The FBI said it was too early to speculate on a motive for the shootings.
Described as a loner, Weise is reported to have expressed admiration for Adolf Hitler on a Nazi website. His fellow pupils said he was sometimes teased because he dressed in black.
The school - close to the Canadian border - has about 300 pupils.
The reservation is home to Native Americans of the Chippewa tribe.