DETROIT -- The Michigan Court of Appeals ruled in favor of the Oxford school district on Thursday in a lawsuit that seeks to hold employees partly responsible for a shooting that killed four students and wounded others in 2021.

The court, in a 3-0 opinion, said lawyers for the families have not offered evidence that shows Oxford staff were the "proximate cause" of the tragedy.

While staff had expressed concerns about Ethan Crumbley, and a meeting was held with his parents on the day of the shooting, it was the teenager who "made the definite and premeditated decision" to take a gun to Oxford High School, the appeals court said.

The court affirmed a lower court decision that said governmental immunity applied. Under Michigan law, immunity is a high hurdle to overcome in lawsuits against a public body or staff. Lawyers typically have to show that gross negligence occurred.

A law firm representing the Oxford families said they'll next ask the Michigan Supreme Court to take an appeal. A separate lawsuit is in federal court.

Crumbley, who was 15 at the time, is serving a life prison sentence. His parents, James and Jennifer Crumbley, are each serving 10-year sentences for involuntary manslaughter. Prosecutors said they had ignored his mental health needs, bought him a gun as a gift and then failed to safely secure it.

Before the shooting, Ethan Crumbley had sketched images of a gun, a bullet and a wounded man on a math paper, accompanied by despondent phrases. The parents were quickly called to a meeting at school but declined to take him home. No one -- parents or staff -- checked the boy's backpack for a gun.