Law enforcement and prosecutors have noted the many warning signs that preceded the massacre at Oxford High School last week, including that 15-year-old Ethan Crumbley was caught Googling ammunition the day before the tragedy and was found with a picture depicting a violent act that said, "The thoughts won’t stop. Help me."

But a former neighbor of James and Jennifer Crumbley, who, like their son, are in the Oakland County jail, told the Detroit Free Press that the Crumbleys started displaying concerning behavior years ago that prompted her to make a complaint with Children's Protective Services. 

"When they were gone, he would come knock on our door," Kayla LeMieux told the newspaper of Ethan when his parents would leave him at home alone to go drinking at bars in 2014 and 2015. "They didn’t leave him with a phone."

Michigan school shooting suspect Ethan Crumbley's parents James and Jennifer

James and Jennifer Crumbley are both facing four counts of involuntary manslaughter.  (Oakland County Sheriff's Office)

LeMieux said that the parents continued leaving their son at home alone even after she made a complaint and confronted them about it. 

"It was really when I finally started to say more, because I was just like, even after calling CPS, they were still doing it and even me saying something to them, they were still like ‘Oh he is fine,'" she told the Detroit Free Press. 

Children's Protective Services did not respond to a request for comment on Monday. 

MICHIGAN SHERIFF IN CONTACT WITH 'PERSON OF INTEREST' CONNECTED TO BUILDING WHERE CRUMBLEYS FOUND, LAWYER SAYS

James and Jennifer Crumbley were arrested in the early hours of Saturday morning and charged with four counts of involuntary manslaughter. 

Oakland County prosecutor Karen McDonald detailed the charges on Friday, saying that Jennifer Crumbley posted about buying a gun for her son in the days before the school shooting and sent a nonchalant message to him after he was caught Googling ammunition in class.  

"Instead of reacting to that as a concerned parent and worried about safety, Mrs. Crumbley texted, 'L.O.L, just I'm not mad. Just next time, don't get caught,'" McDonald said. 

Oxford High School shooting suspect Ethan Crumbley

Ethan Crumbley, 15, allegedly shot and killed four students and injured seven others at Oxford High School.  (Oakland County Sheriff's Office)

James Crumbley bought the 9mm Sig Sauer just four days before the shooting and took him to a gun range for a "mother-son day," according to McDonald. 

ALLEGED MICHIGAN SCHOOL SHOOTER CONVINCED OFFICIALS VIOLENT DRAWINGS WERE HARMLESS PURSUIT

The parents were called to the school on Tuesday morning when a teacher found the disturbing picture, but they refused to take their son home and didn't inform the school about the gun. 

After the shooting began, Jennifer Crumbley texted her son, "Ethan don’t do it," McDonald said. 

McDonald argued in court on Saturday that the Crumbleys were purposely trying to evade law enforcement when they disappeared on Friday, but their attorneys contested that the couple had isolated themselves for their safety. 

The Crumbleys were found in this commercial building in Detroit.

The Crumbleys were found in a commercial building in Detroit. (Fox News)

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Bond was set for each of the Crumbley parents at $500,000, while their son is being held on a $5 million bond. 

Ethan Crumbley is accused of shooting and killing 16-year-old Tate Myre, 14-year-old Hana St. Juliana, 17-year-old Madisyn Baldwin, and 15-year-old Justin Shilling.