The shooter who opened fire Friday morning at Washington state's Marysville-Pilchuck High School played football and was recently named to the homecoming court.
Freshman Jaylen Fryberg was in the school's cafeteria, went up to a table with students, "came up from behind ... and fired about six bullets into the backs of them," witness Jordan Luton told CNN. "They were his friends, so it wasn't just random," Luton said.
The attacker shot five people, killing one, authorities said. A federal law enforcement official, who spoke on condition of anonymity, said the shooter died of a self-inflicted gunshot wound.
Investigators "are confident that there is only one single shooter," Marysville police spokesman Robb Lamoureux told reporters.
Four people were wounded, Sgt. Ryan Dalberg of Everett police told CNN.
Three people were in surgery at Providence Regional Medical Center in Everett, and one person was being transferred to Harborview Medical Center in Seattle, Providence spokeswoman Erin Al-Wazan said.
Three are "very critically ill" with "very serious" injuries, she said. One is in serious condition.
Investigators are tracing a Beretta .40-caliber handgun, the weapon believed used in the attack, a federal law enforcement source with knowledge of the investigation told CNN.
Authorities first learned about the shooting after getting a 911 phone call around 10:30 a.m. (1:30 p.m. ET) from someone inside the school, which is north of Seattle and Everett, Lamoureux said.
It was an early lunch break at the school of about 2,500 students that sits in the heart of Marysville, a small city bisected by the major thoroughfare connecting the region with Vancouver, British Columbia.
Once dubbed "Strawberry City'' because of its berry farms, today Marysville is better known as the home of the Native American Tulalip Resort Casino.
'People started screaming'
Luton was sitting two tables away when the shooting began.
"I heard one loud bang and I was wondering what it was, and then I heard about four or five more. And people started screaming," he said.
Some of the students began to run. But Luton hit the ground.
Fryberg appeared to target one table, where there were about 10 students sitting. "I'm pretty sure he shot at specific people because they were pretty good friends with him," Luton said.
"He put some bullets in the back of the students," he said. "He turned and looked at me and my girlfriend ... and kind of gave us a smirk."
The shooter continued firing as he left the cafeteria, Luton said.
"I have no idea what his motive was because yesterday at football practice, he was all fine, talking .... having a good time," he said. "And then today, just horrible. I don't know what went through his head or what caused him to do it."
By all accounts, Fryberg was a popular student. Just two weeks earlier, he had been named as the high school's freshman homecoming prince, according to a YouTube video of the ceremony and accounts provided by students to CNN.
Fryberg's multiple social media accounts depict him frequently hunting and using rifles.
Those accounts say he was a Native American and a member of the Tulalip tribe.
Luton could not confirm reports that Fryberg had been bullied. But two weeks ago, according to Luton, Fryberg got in a fight after somebody said "something racist" to him.
The school was under lockdown for hours before students were put on buses and sent to a nearby church parking lot, where they were being reunited with their parents.
At first, they thought it was a fire drill
A student locked down inside a classroom told CNN by phone that the shooting began in the cafeteria.
The student, whose name is being withheld, said when the shooting began students initially thought it was a fire drill until teachers told everyone to run into classrooms because there was a shooting.
The student said she hid in a classroom with other students, all of whom are unharmed.
A student who says he was in the cafeteria when the shooting began told CNN he called the police, and then gave his phone to a teacher.
The student described a chaotic and bloody scene, saying blood was "everywhere."
He claimed to know the shooter, describing the gunman as a popular student who recently had been the victim of bullying.
Another student, identified as Austin Taylor, told CNN Seattle affiliate KING that he had just finished eating when he saw the shooter.
"He was just sitting there. Everyone was talking. All of the sudden, I see him stand up, pull something out of his pocket," he said.
"At first, I thought it was just someone making a really loud noise ...like a big loud pop ... until I heard four more after that. And I saw three kids just fall from the table."
Austin said he ducked under a table. When the shooting stopped, he said he looked out and saw the shooter was trying to reload.
"When that happened, I just ran in the opposite direction, and I was out of there as fast as I could," he said.
Medeana Johnson, mother of a boy who is a junior at the school, told CNN affiliate KIRO-TV that her son said a boy opened fire near the cafeteria. She said her son told her he was supposed to be in the cafeteria but stopped to chat with someone and so didn't go in.