Updated October 21, 2022 at 5:21 PM ET

DETROIT — A teenager accused of killing four fellow students and injuring more at a Michigan high school is expected to plead guilty to murder next week, authorities said Friday.

Ethan Crumbley had created images of violence during a classroom assignment last November but was not sent home from Oxford High School in southeastern Michigan. He pulled out a gun a few hours later and committed a mass shooting.

Authorities have pinned some responsibility on Crumbley's parents, portraying them as a dysfunctional pair who ignored their son's mental health needs and happily provided a gun as a gift just days before the attack. They also face charges.

Crumbley, 16, is due in court Monday.

"We can confirm that the shooter is expected to plead guilty to all 24 charges, including terrorism, and the prosecutor has notified the victims," said David Williams, chief assistant prosecutor in Oakland County.

A message seeking comment was left for the boy's lawyers.

Crumbley was 15 when the shooting occurred at Oxford High, roughly 30 miles (50 kilometers) north of Detroit.

His parents had been summoned to school that day to discuss the teen's ominous writings. A teacher had found a drawing with a gun pointing at the words, "The thoughts won't stop. Help me." There was an image of a bullet with the message: "Blood everywhere."

James and Jennifer Crumbley declined to take Ethan home but were told to get him into counseling within 48 hours, according to investigators.

A day earlier, a teacher saw Ethan searching for ammunition on his phone. The school contacted his mother, Jennifer Crumbley, who then told her son in a text message: "Lol. I'm not mad at you. You have to learn not to get caught," the prosecutor's office said.

Ethan Crumbley was charged as an adult with one count of terrorism causing death, four counts of first-degree murder, seven counts of attempted murder and 12 counts related to use of a gun.

A first-degree murder conviction typically brings an automatic life prison sentence in Michigan. But teenagers are entitled to a hearing where their lawyer can argue for a shorter term and an opportunity for parole.

Crumbley's parents face involuntary manslaughter charges

Separately, James and Jennifer Crumbley are facing involuntary manslaughter charges — a rare case of prosecutors trying to make parents accountable for a school shooting. They are accused of making a gun accessible to Ethan and neglecting his need for mental health care.

"Put simply, they created an environment in which their son's violent tendencies flourished. They were aware their son was troubled, and then they bought him a gun," prosecutors said in a court filing.

The Crumbleys said they were unaware of Ethan's plan. They also dispute that the gun was easy to get at home.

Madisyn Baldwin, Tate Myre, Hana St. Juliana and Justin Shilling were killed, while six students and a teacher were injured.

Sheriff says a guilty plea would be a relief for families

Sheriff Mike Bouchard said a guilty plea from Ethan Crumbley would be a relief for families and witnesses.

"At least not to have to go through the pain of painstakingly seeing every bit of evidence, every bit of video and all of the things that would be horrific" at a trial, Bouchard told WDIV-TV.

In court documents, prosecutors have revealed portions of Ethan Crumbley's personal journal. He said his grades were poor and that his parents hated each other and had no money.

"This just furthers my desire to shoot up the school or do something else," the teen wrote.

All three Crumbleys are being held at the Oakland County jail, though Ethan is kept away from adults.

Ven Johnson, an attorney who is suing the Oxford school district, said parents of the shooting victims would withhold comment until after the court hearing.

Copyright 2022 NPR. To see more, visit https://www.npr.org.