Federal authorities believe the high school student behind Monday's massacre in northern Minnesota likely plotted the attack that left 10 dead, including himself.

The shooter, named by authorities as 16-year-old Jeff Weise (search), was a student at the school on the Red Lake Indian Reservation (search).

Weise gunned down his grandfather and the man's girlfriend, put on his grandfather's police-issue belt and bulletproof vest, and drove his marked squad car to a high school, where he began shooting his classmates at will.

Seven other people were wounded in the assault and five were still hospitalized Tuesday, all with gunshot wounds, said Michael Tabman, the special agent in charge of the Minneapolis FBI office. Two were in critical condition with wounds to the head.

Monday's rampage was the nation's worst school shooting (search) since the Columbine High School (search) massacre in 1999, which left 13 people dead.

Aside from the teen's grandfather, Daryl Lusier, and Lusier's companion, Michelle Sigana, Weise's targets appeared random and he apparently acted alone, Tabman said. An unarmed security guard and a teacher also were killed.

Tabman said authorities were still trying to determine Weise's motives. It was still not known what transpired in Weise's grandfather's home that may have set off the rampage.

"The nature of the activities indicate there was some planning," Tabman said, adding that investigations were ongoing.

Authorities believe that Weise shot and killed Lusier and Sigana early Monday afternoon. Weise made off with an unknown number of weapons and a bulletproof vest owned by Lusier, a police officer.

Weise then drove to Red Lake High School (search). The first person he shot and killed was an unarmed secured guard at the building's entrance. Authorities believe Weise immediately started firing upon entering the school building. The first 911 call was made at 2:55 CST.

Weise apparently chased a group of fleeing students and at least one teacher into a classroom, spraying it with bullets. Some of the victims were shot at close range, hospital officials said.

Police said Weise killed himself after exchanging fire with officers. Red Lake Fire Director Roman Stately said the gunman had two handguns and a shotgun.

Parts of the ordeal were captured on videotape. Weise fired numerous rounds in the 10-minute-long spree, causing extensive damage to the school, Tabman said

Reggie Graves, a student at Red Lake, said he was watching a movie about Shakespeare in class Monday when he heard Weise blast his way past the metal detector at the school's entrance, killing a guard.

Then, in a nearby classroom, he heard the gunman say something to his friend Ryan: "He asked Ryan if he believed in God," Graves, 14, said. "And then he shot him." The boy survived.

Minnesota Gov. Tim Pawlenty (search) said a crisis team that included grief counselors was working with the small, tight-knit community. The Department of Education was also in touch with school officials, the governor said in a late-morning news conference.

"It is our intent to have our day or days of remembrance for the victims of this shooting and their families," he said.

"There's not a soul that will go untouched by the tragic loss that we've experienced here," Floyd Jourdain Jr., chairman of the Red Lake Chippewa Tribe, told WCCO-TV of Minneapolis on Tuesday.

Pawlenty said that officials were waiting for input from victims' families, and indicated that state buildings may lower flags. Local tribal officials organized a memorial service.

Disturbing Signs

Authorities were trying to determine what motivated Weise to resort to such an extravagant act of violence. A neo-Nazi Web site indicates the Native American high school student was fascinated with extreme ideas.

A poster to the site who identified himself as Jeff Weise, from the "Red Lake 'Indian' reservation," wrote on March 19, 2004: "It kind of angers me how people pass pre-judgement [sic] on someone if they even so much as say something like 'I support what Hitler did,' without even hearing what you have to say. This goes double if you're ethnic."

The poster went on to describe the Nazi dictator as "a man who deserves great respect."

A month later, using the handle "Todesengel," or "angel of death," the poster wrote that he had been cleared as a suspect after someone threatened an attack on the school on April 20, Hitler's birthday.

Tabman said it hadn't been determined if the writer was actually Weise.

Weise had been placed in the school's Homebound program for some violation of policy, but school board member Kathryn Beaulieu said she didn't know what Weise's violation was and wouldn't be allowed to reveal it even if she did.

Students in that program stay at home and are tutored by a traveling teacher.

A message posted Tuesday on the neo-Nazi Web site, run by the Libertarian National Socialist Green Party, blamed the school massacre on "modern, liberal democratic industrial society."

A forum administrator described Weise as "clearly highly intelligent and contemplative, especially for one so young."

Relatives told the St. Paul Pioneer Press that Weise was a loner who usually wore black and was teased by other kids.

Tabman said investigators were unaware of any grudges Weise may have had.

Relatives also told the newspaper his father committed suicide four years ago, and that his mother was living in a Minneapolis nursing home because she suffered brain injuries in a car accident.

Residents at the home where Weise was believed to have lived with his grandmother declined to comment Tuesday. School was canceled for the day as investigators scoured the building for clues.

High school principal Chris Dunshee said Weise "would not be what I would call an habitual troublemaker," and that he wasn't aware of a lot of teasing.

"I didn't really, I guess, feel that he was teased to the point where something like this would happen," he said.

The Associated Press contributed to this report.