Michigan Attorney General Dana Nessel has offered to “conduct a full and comprehensive review” of actions taken at Oxford High School before last week’s shooting killed four people.

Oxford Community Schools Superintendent Tim Throne said in an open letter to the community Saturday that he would enlist a third-party investigator to determine whether campus personnel could have done more to prevent Tuesday’s attack, which authorities allege was carried out by a 15-year-old student who used a handgun that they said his father had bought days earlier.

Nessel, Michigan’s top prosecutor, suggested Sunday that her state investigators would be best equipped to take on the investigation.

“We have reached out to the attorney for the Oxford Community School District and have offered the services of the Michigan [Department] of Attorney General to conduct a full and comprehensive review of the 11/30/21 shooting and the events leading up to it,” Nessel said in a statement.

“Our attorneys and special agents are uniquely qualified to perform an investigation of this magnitude and are prepared to perform an extensive investigation and inquiry to answer the many questions the community has regarding this tragedy,” she said.

A school district spokesperson could not be immediately reached for comment Monday.

The suspect and his parents had been called into the school office on the day of the crime after a teacher found the teenager with drawings that seemed to depict a gun and a shooting scene, prosecutors said.

His parents declined to take their son home from school, and he was returned to class, officials have said.

The suspect might have had the gun, alleged to have been purchased by his father, in his backpack when they met with school officials last Tuesday.

“We don’t know exactly if that weapon was in his bag, where it was, we just know it was in the school and he had access to it,” Oakland County Prosecutor Karen McDonald told CNN on Monday.

Asked whether school personnel might be prosecuted for failing to find the weapon, McDonald replied: “We haven’t ruled out charging anyone.”

The suspect was charged Wednesday with four counts of first-degree murder, one count of terrorism causing death, seven counts of assault with intent to murder and 12 counts of possession of a firearm in the commission of a felony.

Hana St. Juliana, 14, Madisyn Baldwin, 17, Tate Myre, 16, and Justin Shilling, 17, were killed. Seven other people, including a teacher, were wounded.

A 14-year-old girl with wounds to her neck and her chest was released Sunday from Hurley Medical Center in Flint, the Oakland County Sheriff’s Office said Sunday in a statement. A 17-year-old girl, the last of the injured students still in the hospital, was stable at St. Joseph Mercy Oakland Hospital, the sheriff’s office said.

The suspect’s parents were arrested early Saturday on four counts of involuntary manslaughter after they were found “hiding” in what was described as an art studio near downtown Detroit, the city’s police chief said.

Authorities who had a warrant Monday searched the home of Andrzej Sikora, 65, an artist in Detroit who rents the building where the parents, James and Jennifer Crumbley, were found, said Clarence Dass, the man’s attorney.

Authorities interviewed Sikora on Monday at the Oakland County Sheriff’s Office in Rochester Hills.

“We will vigorously investigate the totality of the situation so a determination can be made if there is any criminality or obstruction of justice involved,” Sheriff Michael Bouchard said in a statement.

Dass said in a statement Sunday that his client is innocent and cooperating.

“Mr. Sikora has not been charged with any crime,” he said. “Nevertheless, upon learning of the Crumbleys’ arrest on December 4, 2021, he voluntarily contacted the Detroit Police Department and Oakland County Sheriff’s Office to provide information.”

The Crumbleys and their son are being held in isolation at the Oakland County Jail, the sheriff’s office said. Bouchard said Saturday that they are checked “multiple times an hour.” 

“There is no indication that any of them were suicidal, but out of an abundance of caution, our amazing corrections team is doing suicide watches on all three of them,” he said.