A 15-year-old boy has been charged with murder and terrorism for a shooting that killed four fellow students and injured seven others at a Michigan high school.
Authorities revealed Ethan Crumbley's parents had been summoned just a few hours before the bloodshed on Tuesday, and Oakland County Sheriff's Lieutenant Tim Willis said during a court hearing the boy recorded video the night before in which he discussed shooting and killing students.
No motive was offered by Oakland County authorities, a day after the violence at Oxford High School, 50 kilometres north of Detroit, but prosecutor Karen McDonald said Tuesday's shooting was premeditated, based in part on a "mountain of digital evidence" collected by police.
"This was not just an impulsive act," McDonald said.
Crumbley was arraigned on charges of murder, attempted murder, terrorism causing death and gun crimes. He is charged as an adult.
Judge Nancy Carniak ordered him to be moved from a juvenile facility to a county jail to be held without bond.
Sheriff Mike Bouchard told reporters that Crumbley's parents were called to the school on Tuesday over "behaviour in the classroom that was concerning".
The teenager remained in school and the shooting occurred a few hours later.
Bouchard offered no details about what had troubled school officials but investigators believe the gun was already in school.
"There is nothing that he could have faced that would warrant senseless, absolutely brutal violence on other kids," the sheriff said.
The shooting should be a wake-up call for new gun laws in a country that has become "desensitised to school shootings", McDonald told reporters.
"We have to do better," she said. "How many times does this have to happen? How many times?"
Officers rushed to the school about lunchtime on Tuesday and arrested Crumbley in a hallway within minutes of the shooting.
His father had bought the 9mm Sig Sauer gun last week, according to the sheriff.
McDonald said charges were being considered against the parents, adding: "Owning a gun means securing it properly and locking it and keeping the ammunition separate."
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.
A teacher who received a graze wound to the shoulder left hospital, but seven students ranging in age from 14 to 17 remained in hospital overnight with gunshot wounds.
After the attack, authorities learned of social media posts about threats of a shooting at the roughly 1700-student school.
All schools in the district are closed for the rest of the week.
Australian Associated Press
