He was taken to the headteacher’s office and his parents were summoned to school. The parents were told to put him in counseling within 48 hours. But they resisted, taking him home immediately and he was instead returned to his classroom.

Neither parent asked him if he had the gun with him, and did not check his backpack, prosecutors said.

The gun was in his backpack and a few hours later, he emerged from a bathroom and started shooting fellow pupils at random.

As news of an “active shooter” at the school was made public, Mrs Crumbley texted her son, saying: “Ethan don’t do it,” prosecutors said.

Fifteen minutes later, Mr Crumbley called 911, reporting that a gun was missing from his house and he believed his son may be the shooter.

The gun had been stored unlocked in a drawer in Mr and Mrs Crumbley’s bedroom.

Ethan Crumbley has been charged with murder and terrorism causing death.

Ms McDonald, the prosecutor, was close to tears as she announced four charges of involuntary manslaughter each against James and Jennifer Crumbley.

She said: “I want to be really clear. These charges are intended to hold the individuals who contributed to this tragedy accountable – and also send a message that gun owners have a responsibility, and when they fail to uphold that responsibility there are serious and criminal consequences.

“We need to do better in this country. We need to say enough is enough. Any individual who had an opportunity to stop this tragedy should have done so. I expect parents to have humanity and step in and prevent a tragedy.”