A prosecutor has filed involuntary manslaughter charges against the parents of a 15-year-old accused of killing four students and wounding seven other people at a Michigan high school.
James and Jennifer Crumbley were each charged with four counts of involuntary manslaughter.
Authorities have said Ethan Crumbley opened fire on Tuesday at Oxford High School, roughly 30 miles north of Detroit.
Seven students and a teacher were shot before Crumbley surrendered to sheriff’s officers.
Three of the students died on Tuesday, and the fourth died on Wednesday in hospital.
The semi-automatic gun used in the shooting was purchased legally by Crumbley’s father last week, according to investigators.
“The parents were the only individuals in the position to know the access to weapons,” Oakland County prosecutor Karen McDonald said on Thursday.
The gun “seems to have been just freely available to that individual”.
She said the parents’ actions went “far beyond negligence”.
Ethan Crumbley has been charged as an adult with two dozen crimes, including murder, attempted murder and terrorism.
Parents in the US are rarely charged over school shootings involving their children, even as most minors get guns from a parent or relative’s house, according to experts.
There is no Michigan law that requires gun owners to keep weapons locked away from children, but Ms McDonald suggested there is more to build a case on.
Sheriff Mike Bouchard said on Wednesday that the parents had met school officials about their son’s classroom behaviour, a few hours before the shooting.
Ms McDonald said information about what had troubled the school “will most likely come to light soon”.
Crumbley stayed in school on Tuesday and later emerged from a toilet with a gun, firing at students in the hallway, police said.
Tim Throne, leader of Oxford Community Schools, said the high school looks like a “war zone” and will not be ready for weeks, but he repeatedly credited students and staff for how they responded to the violence.
“To say that I am still in shock and numb is probably an understatement. These events that have occurred will not define us,” he said.
“I want you to know that there’s been a lot of talk about the student who was apprehended, that he was called up to the office and all that kind of stuff. No discipline was warranted,” Mr Throne said.
“There are no discipline records at the high school. Yes, this student did have contact with our front office, and yes, his parents were on campus November 30.”