Policies and procedures that could have prevented a mass shooting that left four students dead at a Michigan high school last year were approved earlier but never implemented, two former school board officials said Monday.

Tom Donnelly and Korey Bailey, who recently resigned as Oxford Community Schools' board president and treasurer, told reporters that a threat assessment policy had been adopted by the district in 2004 and was later updated.

Bailey said he first learned about the policy in August. He calls it "an operational guide for preventing school violence" that defines the roles of teachers, counselors and other staff when there are indications of a possible threat. He also said it never was put into practice in Oxford school buildings prior to Nov. 30, 2021.

OXFORD HIGH SCHOOL TEACHERS WHO FLAGGED SHOOTER'S 'CONCERNING' WARNING SIGNS WERE IGNORED: ATTORNEY

Wednesday will mark the one-year anniversary of the shooting at Oxford High School that also wounded six other students and a teacher.

Prosecutors have said Ethan Crumbley used a semi-automatic handgun to open fire on other teenagers in the hallway at the school roughly 30 miles (50 kilometers) north of Detroit. The four students who were killed were 16-year-old Tate Myre, 14-year-old Hana St. Juliana, 17-year-old Madisyn Baldwin and 17-year-old Justin Shilling.

School officials have been criticized by the county sheriff and Oakland County Prosecutor Karen McDonald for not alerting a school resource officer about their concerns with Crumbley and not searching the teen's backpack before allowing him to return to class about three hours before the shooting.

Former Oxford Community Schools Board President Tom Donnelly presents a binder labelled "Enhancing School Safety Using a Threat Assessment Model, an operational guide for preventing targeted school violence" at a Monday press conference. Donnelly was one of multiple school officials to note that guidelines the publication listed were not properly followed in the leadup to the 2021 Oxford High School shooting. (Daniel Mears/Detroit News via WHD)

The day before the shooting, a teacher saw Crumbley, then 15, looking at ammunition on his phone while in class. School officials left a voicemail informing his mother about it. On the morning of the shooting, Crumbley’s parents were summoned to the school and confronted with his drawings, which included a handgun and the words: "The thoughts won’t stop. Help me."

Authorities said his parents, James and Jennifer Crumbley, refused to take him home after the 13-minute meeting and were told to get him counseling.

Widely accepted best practices for threat assessment have been adapted from Secret Service guidance developed in the years since the 1999 Columbine school massacre. The agency’s National Threat Assessment Center recommends multidisciplinary teams of school administrators, security and mental health professionals be established to assess whether a student would be helped by counseling, should be reported to police, sent back to class or something in between.

Donnelly likened it to measures that districts across the country use to prevent fire deaths in schools.

"When you don’t want kids to die in a fire you create processes and procedures ... and you’re making them go through training," he said. "We never did that with this (threat assessment) policy and guideline," Donnelly said. "We never ever did it, and hence when we needed to implement it, it wasn’t there. Someone may have had some training about it, but we never created a team. We never had the team activated. We never practiced the team. We never did drills."

Oxford Community Schools Board of Education said Monday that a third-party review of events leading up to, during and after the shooting will help in understanding the facts.

"We ask the public to allow this important review process to take place so the facts can be brought to light in a clear, accurate, and impartial manner," current board president Dan D’Alessandro said in a release.

Ethan Crumbley, now 16, pleaded guilty last month to terrorism and first-degree murder charges. Prosecutors have said they’ll seek a life sentence with no chance for parole.

OXFORD SCHOOL SHOOTING: ETHAN CRUMBLEY PLEADS GUILTY TO CHARGES

Oakland County Prosecutor Karen McDonald also charged his parents with involuntary manslaughter, accusing them of failing to keep the gun used in the shooting secure at home and failing to reasonably care for their son when he showed signs of mental distress. The Crumbleys face trial next year.

Detroit attorney Ven Johnson, who represents some victims' families in a civil lawsuit against the district, has said some teachers and a counselor at the school were aware of Ethan Crumbley's troubling interest in guns and violence months before the mass shooting.

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The resignations of Donnelly and Bailey are the latest exoduses from the district. Schools Superintendent Ken Weaver announced he is on a medical leave that will take him to his resignation on Feb. 21. Weaver was appointed superintendent in March after his predecessor, Tim Throne, retired.