A teenager has been killed and eight other pupils injured after two students opened fire at a school in Colorado.
The suspected shooters have both been arrested.
Police said the pair walked into the Highlands Ranch School in Denver and began shooting students in two classrooms.
Within minutes, officers entered the school and arrested the two suspects after a struggle.
Pupils and staff at the school recalled that as the gunfire rang out, students ran through the halls shouting ‘School shooter!’
Some said they wondered at first if it was a joke or a drill.
Sophia Marks, 16, told reporters: ‘At the moment no one really knew what was going on so I didn’t know they were bullets.
‘I just kind of saw like flashes and we heard bangs.’
Chris Elledge, 15, said his teacher told the class to hide behind weight equipment in the room, where they stayed until police arrived.
“They [officers from the sheriff’s department] busted in the room, and they were asking if there was any suspects in the room, if we were OK, and they escorted us out to go out to the front of the building,” he said.
Three hospitals reported treating eight people in connection with the attack, including two who were listed in serious condition.
Governor Jared Polis said in a statement that he was making state public-safety resources available to help secure the site and evacuate students.
He added: ‘The heart of all Colorado is with the victims and their families.’
The shooting comes nearly three weeks after neighbouring Littleton marked the grim 20th anniversary of the Columbine school shooting that left 13 people dead.
The two schools are separated by about seven miles south of Denver.