this is sad
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.
'Grinning'
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.
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.