By Sky News US Team
A school student who went on a shooting spree before killing himself wrote a series of chilling tweets in the months before he ran amok with a gun.
Jaylen Fryberg opened fire in a cafeteria, murdering one teenager and critically injuring three others at Marysville-Pilchuck High School in Marysville, about 35 miles north of Seattle, Washington.
The gunman was reported to be initially "quiet" before opening fire on fellow diners.
Each of the 15-year-old's victims have gunshot wounds to the head, and the two teenage boys hurt in the attack, Nate Hatch, 14, and Andrew Fryberg, 15, were cousins of the killer.
The teenage girl who remains in a critical condition has been named locally as Shaylee Chuckulnaskit, whose uncle told local TV station KIRO that "he wasn't sure she'd make it".
Calvin Walker, who was in the cafeteria at the time, added: "I didn't think there was any hope of them being OK because of how close he shot them. I knew it was going to be bad."
Gallery: Students Distraught After High School Shooting
Police have said two people are dead, including an armed student, after a shooting at a high school north of Seattle
The attacker was named as Jaylen Fryberg
He had made a number of emotional posts on Twitter in recent days
The attacker took his own life in the incident at Marysville-Pilchuck High School in Washington state
Three young people are in a "very critical condition" and one other is in a serious condition
Witnesses said the freshman took a gun out of his backpack in a cafeteria and opened fire
TV footage showed students being evacuated from the school, which has about 2,500 enrolled
Armed police conducted room-to-room searches with guns drawn
Another student said: "At first I thought it was just someone making a really loud noise, like a bag, like a pretty loud pop, until I heard four more after that, and I saw three kids just fall from the table like they were falling to the ground dead."
Eyewitnesses have told reporters that a new teacher at the school, Megan Silberberger, tried to intervene during the shooting spree.
They claim the Social Studies tutor managed to restrain his arms, but during the struggle, the gun fired again, leaving Fryberg with a fatal wound to the neck.
The teenager left a series of posts on Twitter before his attack which painted a picture of a boy who was familiar with using weapons.
Next to an Instagram picture of him holding a hunting rifle, he wrote: "Probably the best BirthDay present ever! I just love my parents!!!!"
In August, he issued a threat to an apparent love rival, saying: "Your not gonna like what happens next."
On 18 September he wrote: "Did you forget she was my girlfriend?" and later tweeted: "Dude. She tells me everything. And now. I... hate you! Your no longer my brother."
On Tuesday, one of a series of tweets said: "It breaks me... It actually does... I know it seems like I'm sweating it off... But I'm not.. And I never will be able to."
In his last post on Thursday, Fryberg stated: "It won't last... It'll never last..."
Fryberg was crowned the school's freshman "homecoming prince" just a week ago, according to some US media.
On Friday night, a candlelit vigil was held for the victims of the school shooting in a nearby church.
The high school is going to be closed throughout next week out of respect for the injured.