Jennifer and James Crumbley, the parents of Ethan Crumbley, a teenager accused of killing four students in a shooting at Oxford High School, appear in court for a preliminary examination on involuntary manslaughter charges in Rochester Hills, Mich., Tuesday. (AP photo)

ROCHESTER HILLS, Mich. (AP) — A day before four students were killed at a Michigan school, the mother of the teenager charged with carrying out the mass shooting sent him a text message asking if he had showed teachers a “pic of your new gun,” an investigator testified Tuesday.

The text was one of several between Jennifer and Ethan Crumbley on Nov. 29 after school officials left a voicemail informing her that the 15-year-old was looking up ammunition on his phone.

A judge must decide if there’s enough evidence to send Jennifer Crumbley and her husband, James Crumbley, to trial on involuntary manslaughter charges. It’s a low threshold under Michigan law, but this case is highly unusual because parents are rarely held criminally responsible for teens accused in mass school shootings.

The Crumbleys, who are in jail on $500,000 bond, are accused of making a gun accessible to Ethan and failing to intervene when he showed signs of mental distress at home and at school. Four students were killed and others were wounded in the Nov. 30 attack at Oxford High School, which is roughly 30 miles (50 kilometers) north of Detroit.

The school left a voicemail for Jennifer Crumbley the day before the attack informing her that a teacher was concerned about Ethan’s ammunition search on his phone.

In court, Ed Wagrowski, a computer crimes investigator in the Oakland County sheriff’s office, read aloud a series of texts exchanged between mother and son.

“Seriously?? Looking up bullets in school??” Jennifer Crumbley wrote.

Her son replied: “Oh yeah. I already went to the office for that. All I did was look up a certain caliber at the end of class because I was curious. Completely harmless.”

“Did you at least show them a pic of your new gun?” Jennifer Crumbley asked.

“No I didn’t show them a pic. My God,” he wrote back.

The Crumbleys’ attorneys insist the couple didn’t know their son might be planning an attack and didn’t make the gun easy to find in their home.

Prosecutor Karen McDonald said she was trying to show that the couple committed gross negligence. Her first witness was the manager of a stable where the Crumbleys kept two horses and visited three to four times a week.

McDonald’s questions were intended to show that the parents seemed more concerned about the health of a horse that had a leg fungus than the “disturbed” mental health of their son.

Wagrowski read aloud text messages written by Ethan to his mother last March. The teen said their house was haunted and a demon was throwing bowls. Jennifer Crumbley was riding a horse and didn’t respond that day, the investigator said.

On the morning of the shooting, Jennifer and James Crumbley were summoned to the school and confronted with Ethan’s drawings, which included a handgun and the words, “The thoughts won’t stop. Help me.” Authorities said the parents refused to take him home after the 13-minute meeting and were told to get him counseling.

Amanda Holland, a co-worker at a real estate company, said Jennifer Crumbley shared a picture of the drawings when she returned to work from the school meeting.

“I told her I thought it was scary. She agreed,” Holland testified.