A Michigan jury has convicted a teenage killer’s mother of involuntary manslaughter in a first-of-its-kind trial to determine whether she had any responsibility in the deaths of four students in a 2021 school shooting.

Prosecutors said Jennifer Crumbley was grossly negligent and could have foreseen the violence before her son opened fire at Oxford High School.

She failed to tell school officials that the family had a new 9mm handgun that Ethan Crumbley ultimately used to kill other teenagers. The mother was accused of making the gun accessible at home and not tending to her son’s mental health.

The school was concerned about a macabre drawing of a gun, bullet and wounded man on the 15-year-old’s maths assignment, accompanied by desperate words: “The thoughts won’t stop. Help me.”

But Ethan was allowed to stay in school November 30, 2021, following a brief meeting with the parents, who did not take him home.

The teenager pulled the gun from his backpack that afternoon and shot 10 students and a teacher, killing four students. No one had checked his backpack.

The gun had been purchased just four days earlier on Black Friday by his father, James Crumbley. Jennifer Crumbley took her son to a shooting range that same weekend.

Jennifer Crumbley, 45, told jurors that she would not have done anything differently but wished her son had “killed us instead”. She denied that he had mental health problems.

James Crumbley 47, is scheduled for trial in March on the same involuntary manslaughter charges.

Ethan, now 17, is serving a life sentence for murder and terrorism.