A 17-year-old Minnesota student is believed to have shot his grandfather and another woman, driven a pickup truck to his high school, then shot a security guard, a teacher, and five classmates at about 3pm local time on Monday (2100 UTC). As many as 14 others were injured before the teenager reportedly shot himself dead.

One witness said the gunman was "grinning and waving".

"I looked him in the eye and ran in the room, and that's when I hid," Sondra Hegstrom told The Pioneer of Bemidji. "You could hear a girl saying, 'No, Jeff, quit, quit. Leave me alone. What are you doing?"

Today's incident had the highest death toll in a US school shooting since the Columbine High School massacre on April 20, 1999, during which 15 people were shot in Jefferson County, near Littleton, Colorado.

There was no apparent motive for the shooting.

"It will probably take us throughout the night to really put the whole picture together," said FBI spokesman Paul McCabe, at a briefing to the press. "We do have evidence that we believe that the shooter is dead," he continued, "we believe he was acting alone."

Reporters were asked to leave the area, located on The Red Lake reservation, by tribal authorities.

"The events that took place today involving the shootings at the Red Lake High School make this one of the darkest and most painful occurrences in the history of our tribe," said Floyd Jourdain Jr., Chairman of the Red Lake Band of Chippewa Indians.

The Red Lake band is made up of about 5,100 people, living on 825,000 acres of land in the northern part of the state.

Minnesota's last school shooting was in September 2003, when two students were fatally shot at Rocori High School.

The incident had statewide implications, causing a hearing on expansion of tribal gaming in Minnesota to be canceled for the day.

"We ask Minnesotans to help comfort the families and friends of the victims who are suffering unimaginable pain by extending prayers and expressions of support," said a statement from Minnesota Gov. Tim Pawlenty.