Hours before he allegedly opened fire on his Oxford High School classmates on Tuesday, Ethan Crumbley was summoned to a school meeting along with his parents.

According to authorities, a teacher had spotted a school assignment that morning on the 15-year-old’s desk that included a drawing of a semi-automatic handgun pointing at the words, “The thoughts won’t stop, help me.” There was also a drawing of a bullet, with the words, “Blood everywhere.” Between the two messages was a drawing of a person who appeared to be shot twice and bleeding, and a laughing emoji. Further down, the words: “My life is useless,” and “The world is dead.”

One day earlier, a school staffer noticed the sophomore was using his phone to search online for ammunition.

In the room with Crumbley in that meeting was his backpack, which authorities now believe contained a recently purchased semi-automatic handgun and ammunition.

Despite the disturbing drawings and reports from teachers, Crumbley was allowed to return to class Tuesday. His backpack wasn’t searched by either his parents or school officials at the meeting. Not long afterward, authorities say, the teen used the weapon to kill four students and injure seven others before he was captured.

The new details, revealed Friday by Oakland County Prosecutor Karen McDonald, accompanied a slew of criminal charges levied against the defendant’s parents.

But they also raise questions about whether Oxford High School officials missed a critical opportunity to squelch the violent rampage that followed. Instead of calling law enforcement or removing the boy from school, officials allowed him to return to class.

A message left for Oxford High Principal Steven Wolf on Friday was not immediately returned.

Oxford Superintendent Tim Throne issued a video statement Thursday night, before McDonald released the details of the alleged shooter’s writings. In the video, Throne said “no discipline was warranted” against Evan Crumbley as a result of the morning school meeting. His video did not address the more specific questions of whether school officials should have notified law enforcement or taken other action, short of discipline, to have the teen’s mental-health status checked before he could return to school.

McDonald, the prosecutor, and a former high school English teacher, ventured her own views on those questions Friday.

“I’m not going to give you a political answer and I’m not going to cover for anybody; I’m just going to say what I think: Of course, he shouldn’t have gone back to that classroom,” she said at a news conference to announce the criminal charges against the parents. “I believe that is a universal position.”

McDonald told the media she isn’t sure if the school faced criminal liability. But in at least one prior school shooting, schools paid a multi-million dollar settlement for not taking more proactive steps to prevent a tragedy.

“Looking at that drawing,” she said of the teen’s note, “it’s impossible not to conclude that there was a reason to believe he was going to hurt somebody.”

“I am angry as a mother. I’m angry as a prosecutor. I’m angry as a person that lives in this country,” McDonald said. “There were a lot of things that could have been so simple to prevent (the shooting).

“Yes, there was a perfectly-executed response (during and after the shooting), and he was apprehended immediately,” she said. “And we have great law enforcement and good training. But, like I said before, four kids were murdered and seven more injured.”

Bridge Michigan spoke with several state education officials Friday, none of whom were willing to publicly talk about Oxford’s handling of Crumbley before the rampage. State Superintendent Michael Rice declined comment, citing the ongoing criminal investigation into the shooting.

These officials said Michigan schools are required to report crimes to local police departments, but there is no requirement to report incidents that may fall into a gray area where a threat, however disturbing, is less than specific, such as a drawing and note.

But nothing stops schools from reporting suspicions to police, or sending a child home.

“Any individual who had the opportunity to stop this tragedy should have done so,” McDonald said. “The question is, what did they know? And when did they know it?”

Schools can search students’ lockers because lockers are school property, but backpacks are private property, and can only be searched if there is “reasonable suspicion” of injury or wrongdoing, according to the website of the Michigan State University College of Law,

“This means that a school official cannot just randomly stop a student in the hall and force that student to hand over their backpack for a search,” the website said. “That student must have given the school a legitimate reason for searching the backpack, such as potentially having a weapon or illegal drugs in the backpack.”

The Oxford shootings raise the question of whether Crumbley’s note and drawing, together with his searching for ammo, met that standard.

Authorities say they believe the handgun used in the shooting, which had been purchased for the 15-year-old by his father on Black Friday as an early Christmas present, was stashed in Crumbley’s backpack on Tuesday, before he removed it in a bathroom and emerged into a hallway shooting.

Schools can be sued in the wake of school shootings. After the 2018 shooting at Marjory Stoneman Douglas High School in Parkland, Fla., families of the victims filed dozens of lawsuits against school officials  they argued could have prevented the attack.

The Parkland gunman had a history of disciplinary problems, and had been the source of a tip to the F.B.I. saying he might become violent at school. Parents reached a $25 million settlement with the school district and a separate $130 million settlement with the federal government.