(PONTIAC) - Prosecutors on Thursday played a recording of a desperate 911 call by the father of a Michigan school shooter as they tried to show jurors how he quickly determined that the teen might be the killer.

It was the last piece of evidence presented on the first day of James Crumbley's involuntary manslaughter trial in suburban Detroit. He isn't accused of knowing that 15 year old Ethan planned to shoot up Oxford High School, but prosecutors allege that his gross negligence was a cause of the tragedy.

Four students were killed and seven people were wounded on November 30, 2021. The shooter's mother, Jennifer Crumbley, was found guilty of the same involuntary manslaughter charges last month.

The Crumbleys are the first U.S. parents to be charged with having criminal responsibility for a mass school shooting committed by a child. Assistant Prosecutor Marc Keast told the jury this case isn’t about bad parenting. He says we are talking about preventable mass murder.

Keast emphasized a series of key points during his opening statement. He noted that James Crumbley, accompanied by his son, bought a Sig Sauer 9 mm handgun four days before the shooting. The father never told school staff about the purchase, or a trip to a shooting range that same weekend, when he and his wife were summoned to discuss a disturbing drawing on Ethan’s math assignment on the day of the shooting.

Prosecutors also allege that the Crumbley's ignored their son’s pleas for help for mental distress. Ethan told a friend that James Crumbley’s response was to tell the boy to “suck it up,” according to text messages introduced as evidence.