James Crumbley, the father of Michigan mass shooter Ethan Crumbley, failed to adequately secure firearms and ammunition, a detective alleged during Tuesday court proceedings from Crumbley's involuntary manslaughter trial.

Detective Adam Stoyek testified that Crumbley kept his guns in a safe with the combination "0-0-0" - though Crumbley initially told police the combination was "0-0-0-0." Stoyek further alleged that Crumbley stored a box of .22 caliber ammunition under the gun case, along with two magazines and a holster, CNN  reported.

James and his wife Jennifer Crumbley were each charged with four counts of involuntary manslaughter after their son killed four classmates and injured seven others at Oxford High School in a November 2021 shooting.

Michigan prosecutors' decision to charge a school shooter's parents with homicide-level crimes  is unprecedented but many advocates believe this could prove to be an effective strategy for combating the country's mass shooting epidemic.

Jennifer Crumbley was found guilty on all four counts of involuntary manslaughter last month and could face up to 15 years in prison. During her trial, her attorneys argued that James was responsible for securing the family's firearms, ABC News reported.

During Stoyek's testimony he described Crumbley as "cooperative" with the police. In the immediate aftermath of the shooting, Crumbley told Stoyek where the guns were stored in his home.

"I'm completely open, and I want you guys to do what you have to do," he said in a filmed police interview.