Fifteen-year-old Ethan Crumbley, who was charged with murder and terrorism for a shooting that left four of his classmates dead, recorded a video night before the violence, officials say.
A 15-year-old boy who is suspected of shooting dead four fellow students and wounding several others in the US state of Michigan recorded a video night before the violence in which he discussed targeting students, officials have said.
No motive was offered by Oakland County authorities on Wednesday, a day after the violence at Oxford High School, roughly 50 kilometres north of Detroit but prosecutors charged the teenager Ethan Crumbley with murder and terrorism.
The video was not posted online and there was no advance warning, according to Oakland County Sheriff Michael Bouchard.
"It's clear that he came out with the intent to kill people. He was shooting people at close range, oftentimes towards the head or chest," said Bouchard.
Prosecutor Karen McDonald said the shooting was premeditated, based in part on a "mountain of digital evidence" collected by police.
Meanwhile, a judge ordered the boy be moved from a juvenile facility to a county jail where he will be held without a bond.
Parents summoned before shooting
Sheriff Bouchard told reporters that the boy’s parents had been summoned to the school before the violence.
Bouchard wouldn't discuss details of the behaviour school officials were concerned about.
The teen was in the meeting with his parents, Bouchard said.
The four students who were killed were identified as 16-year-old Tate Myre, 14-year-old Hana St. Juliana, 17-year-old Madisyn Baldwin, and 17-year-old Justin Shilling.
US 'de-sensitised to school shootings'
Prosecutor McDonald said the shooting should be a wake-up call for new gun laws in a country that has become "de-sensitised to school shootings."
"How many times does this have to happen? How many times?"
Crumbley's father bought the 9 mm Sig Sauer gun last week, according to officials.
McDonald strongly suggested that more charges will be filed.
"We are considering charges against both parents and we will be making a decision swiftly," she said.
"Owning a gun means securing it properly and locking it and keeping the ammunition separate," she said.