A 15-year-old student has been arrested after two of his classmates were killed in a shooting at a US high school, with a further 19 injured.
Hundreds were sent fleeing for safety as shots rang out at Marshall County High School in Kentucky on Tuesday.
Students were seen jumping into cars and running down a highway, some not stopping until they reached a McDonald's restaurant more than a mile away.
Police later led a teenager away in handcuffs and said the suspect will be charged with murder, following the US's first fatal school shooting of 2018.
"They was running and crying and screaming," said Mitchell Garland, who provided shelter to between 50 and 100 students inside his nearby business.
"They was just kids running down the highway. They were trying to get out of there."
Two 15-year-olds were killed. A girl died at the scene, and a boy died later at a hospital, the governor Matt Bevin said, adding that all of the victims are believed to be students.
Half a dozen ambulances and numerous police cars converged on the school, along with officers carrying assault rifles.
Parents left their cars on both sides of an adjacent road, desperately trying to find their teenagers.
Police did not release his identity, nor did they describe a motive.
"This is a wound that is going to take a long time to heal. For some in this community will never fully heal," Mr Bevin said.
Five of the wounded were flown about 120 miles to Nashville, Tennessee's Vanderbilt University Medical Centre, spokeswoman Tavia Smith said.
Mr Bevin said earlier in a statement that "it is unbelievable that this would happen in a small, close-knit community like Marshall County".
Marshall County High School is about 30 minutes from Heath High School in Paducah, Kentucky, where a 1997 mass shooting killed three and injured five.
Michael Carneal, then 14, opened fire there about two years before the fatal attack at Columbine High School in Colorado, ushering in an era when mass school shootings have become much more common.
