On the morning of November 30, 2021, Ethan Crumbley drew violent pictures of a gun, bullet, and a wounded man on his high school maths assignment.
"Blood everywhere," the 15-year-old wrote on the page. "The thoughts won't stop. Help me," he pleaded under a geometry exercise.
Concerned staff at the Oxford High School in Michigan called his parents in for a meeting but they did not take the boy home.
Just a few hours later, Ethan pulled a handgun from his backpack and shot four of his classmates dead, while wounding six others and a teacher.
The gun was the 9mm Sig Sauer that his father had purchased with him just four days earlier, and which his mother had him practice using at a shooting range.
Ethan is now serving a life sentence in prison after he pleaded guilty to terrorism and first-degree murder in December.
Jurors have also convicted his mother, Jennifer Crumbley, of four involuntary manslaughter charges in what is regarded as the first US prosecution of a parent in connection to a mass school shooting by their child.
Her husband, James Crumbley, was also charged with involuntary manslaughter and is set to stand trial next month.
So what ramifications will this landmark ruling have? Could it pave the way for other parents to be held responsible for their child's crimes? We have spoken to an American legal expert to find out.
But first, let's take a look at why Ethan's mother was found responsible.
Why was the mother found responsible?
Even though Jennifer Crumbley did not pull the trigger, she was held responsible for not safely securing the gun and ammunition at home, as well as failing to seek support for her son's mental health.
Prosecutors said the 45-year-old mother had a duty under Michigan law to prevent her teenage son from harming others.
Outside the courthouse on Tuesday (local time), the jury forewoman said the guilty verdict was influenced by evidence that Jennifer Crumbley was the last adult to possess the gun.
"[That] really hammered it home," she said, while declining to give her name.
The jury was shown video images during the trial of Jennifer Crumbley leaving the shooting range with the gun in the box.
"You saw your son shoot the last practice round before the [school] shooting on November 30. You saw how he stood … He knew how to use the gun," assistant prosecutor Marc Keast said while cross-examining the mother last week.
"Yes, he did," Jennifer Crumbley replied.
Her lawyer, Shannon Smith, argued there were no real warning signs that Ethan would kill his classmates and that the crimes were "unforeseeable".
"Can every parent really be responsible for everything that their children do?" she asked jurors in her closing arguments.
Jennifer Crumbley, who testified in her own defence, said her son had been anxious about being accepted into college and what he would do with his life, but she did not think his problems merited seeing a psychiatrist.
"We would talk. We did a lot of things together," she said. "I trusted him, and I felt I had an open door. He could come to me about anything."
But in a journal found by police, Ethan wrote that his parents would not listen to his pleas for help.
"I have zero help for my mental problems and it's causing me to shoot up the ... school," he wrote.
School officials insisted they would not have agreed to keep Ethan on campus the day of the shooting if the parents had shared information about the new gun.
"He literally drew a picture of what he was going to do," prosecutor Karen McDonald said. "It says, 'Help me.'"
What ramifications could the ruling have?
Professor of law at the University of Michigan Ekow Yankah says Jennifer Crumbley's trial sets a "contentious" precedent for holding parents accountable for their child's wrongdoings.
"Now you've given prosecutors a new tool," he says.
"For many other parents, there's going to be a worry, even in cases less extraordinary [in which] the parent is trying to keep their son out of trouble, maybe out of gang behaviour, maybe struggling with drugs and alcohol.
"The question is where exactly will the law draw the line?"
Loading...He says the maximum 15-year prison term for involuntary manslaughter could be used by prosecutors as leverage against negligent parents.
"[They'll] tell them if you don't agree to a plea bargain, I will try this case and send you to prison for much longer."
While there have been prior cases where parents were held responsible for their direct negligence, Professor Yankah says "it's quite an extraordinary step forward" to hold them responsible for their child's actions.
"One the one hand, the facts were hard enough [in the Crumbley case] that I understand why a prosecutor would want to try it," he says.
"On the other hand, there's a moral intuition that at some point you can't be responsible for somebody else's behaviour. I think in both society and the prosecutor's office, people are going to be really torn about that."
Professor Yankah says he's also concerned the law would be disproportionately used on people from underprivileged groups.
"In America, whenever there is an amping up of criminal law, it almost certainly ends up aiming it at the most politically vulnerable, the poor ... and the black and the brown," he says.
"It'll have a racial impact in less spectacular cases where somebody's child is misbehaving, they can't quite control their child, the child does something awful, but instead of being national news, it'll be a quiet plea bargain."
ABC/wires