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[Breaking news update, published at 7:21 p.m. ET]

James Crumbley, the father of the teenager who killed four students at a Michigan high school in 2021, was found guilty of involuntary manslaughter in a trial that comes a month after the shooter’s mother was convicted of the same charges.

James Crumbley was convicted of four counts of involuntary manslaughter, a charge that carries a maximum punishment of up to 15 years in prison, which would run concurrently.

The cases against the shooter’s parents stood as a test of the limits of who’s responsible for a school shooting.

[Original story, last published at 11:19 a.m. ET]

Jury deliberations resumed Thursday in the manslaughter trial of James Crumbley, the father of the teenager who killed four students at a Michigan high school in 2021, in a case tried just a month after the shooter’s mother was convicted of the same charges.

Crumbley is charged with four counts of involuntary manslaughter and faces up to 15 years in prison if convicted. The jury deliberated for about an hour Wednesday.

Prosecutors in closing arguments Wednesday said James Crumbley was “grossly negligent” because he bought a SIG Sauer 9mm gun for his son days before the attack, failed to properly secure it, ignored his son’s deteriorating mental health and did not take “reasonable care” to prevent foreseeable danger.

“James Crumbley is not on trial for what his son did,” Oakland County Prosecuting Attorney Karen McDonald said. “James Crumbley is on trial for what he did and what he didn’t do.”

In response, defense attorney Mariell Lehman asserted the prosecution’s case lacked evidence and was based on “assumptions and hindsight.”

“You heard no testimony and you saw no evidence that James had any knowledge that his son was a danger to anyone,” she said.

The deliberations come more than two years after Ethan Crumbley, then 15, used the SIG Sauer 9mm to kill four students and wound six students and a teacher at Oxford High School on November 30, 2021.

The cases against the parents represent a test of the limits of who is responsible for a mass shooting. Prosecutors aiming to expand the scope of blame in mass shootings have used a novel legal strategy by arguing the parents are personally responsible for the deaths because they got their son a gun and ignored signs of his declining mental health.

Parents have previously faced liability for their child’s actions, such as with neglect or firearms charges, but Jennifer Crumbley’s guilty verdict was the first time a school shooter’s parent was held directly responsible for the killings. She is set to be sentenced on April 9.

Ethan was sentenced last year to life in prison without parole after pleading guilty to terrorism causing death, four counts of murder and 19 other related charges. He did not testify in either of his parents’ trials, as his attorneys said he would invoke his Fifth Amendment right to silence.

Mental health and gun security were key focuses in the trial

James Crumbley’s trial began last week and has been altogether similar to his wife’s trial, featuring many of the same shooting survivors, police investigators and school employees.

However, prosecutors focused more closely on his purchase of the firearm and how he stored it, while featuring less evidence about his personal life and interests. Most notably, Jennifer Crumbley took the stand in her own defense at her trial, pushing blame onto others and expressing no regrets.

In contrast, James Crumbley declined to testify. “It is my decision to remain silent,” he said in court.

The prosecution rested its case after calling 15 witnesses over the past week. The defense called one witness, James Crumbley’s sister Karen, who testified that she had spent several days with the Crumbley family in April and June 2021 and did not notice anything concerning.

How the murder weapon was secured and how the shooter gained access to it has been a key point of contention.

According to testimony, James purchased the weapon for his son on Black Friday in 2021, and he later told investigators he hid it in a case in his armoire, with the bullets hidden in a different spot under some jeans.

“I will have to find where my dad hid my 9mm before I can shoot the school,” the then-15-year-old wrote in a journal entry before the shooting.

A detective said that a cable lock sold with the SIG Sauer was found still in its plastic packaging, and no other firearm locking mechanisms were found in the home. However, the defense has questioned whether a different locking mechanism may have been used to secure the firearm.

In addition, two other firearms in the home – a .22-caliber Derringer and a .22-caliber KelTec – were locked in a gun safe in the parents’ bedroom dresser, but the combination to unlock the safe was “0-0-0,” the default factory setting, the detective testified.

Prosecutors also argued James Crumbley missed clear warning signs that his son needed help.

In an April 2021 text to a friend, the shooter said he was hearing people talking to him and seeing someone in the distance.

“I actually asked my dad to take (me) to the Doctor yesterday but he just gave me some pills and told me to ‘Suck it up,’” the shooter wrote.

Lehman, the defense attorney, argued there was no evidence the shooter actually asked for help and no evidence his father declined to help. “James had no idea that his son was having a hard time,” she said.

Further, on the morning of the shooting, both parents were called into school to discuss Ethan’s disturbing writings on a math worksheet, including the phrases “help me,” “blood everywhere” and “my life is useless” and drawings of a gun and bullet.

Oxford High School counselor Shawn Hopkins testified he recommended the parents take Ethan out of school to get mental health treatment the day of the shooting, but Jennifer Crumbley said they wouldn’t be able to do so because they had work. James Crumbley did not protest, the counselor testified.

The school employees and the parents agreed to keep Ethan in class for the day, the employees testified. About two hours later, the teenager took the gun out of his backpack and opened fire, killing Madisyn Baldwin, 17; Tate Myre, 16; Hana St. Juliana, 14; and Justin Shilling, 17.

Prosecutors said the shooting could have been prevented if James or Jennifer Crumbley had listened to the counselor’s recommendation and taken their son out of school, or if they had mentioned to the employees they had just purchased him a gun.

“James Crumbley was presented with the easiest, most glaring opportunities to prevent the deaths of these four students, and he did nothing,” McDonald said. “He did nothing – over and over and over again.”

Lehman disagreed, saying James did not know his son had gained access to the weapon and did not believe there was an imminent, immediate threat of danger.

“James Crumbley had no idea what his son was capable of, he had no idea what his son was planning, and he had absolutely no idea that his son had access to those firearms,” Lehman said.

CNN’s Nicki Brown contributed to this report.