Concerns regarding the behavior of the Michigan high school shooting suspect before to the tragedy have been revealed by investigators.

Two instructors noticed troubling behavior from senior Ethan Crumbley in the days leading up to the deadly Michigan high school shooting, prompting two meetings with him, including one with his parents only hours before the atrocity, according to a sheriff.

Crumbley, 15, was charged as an adult on Wednesday with terrorism, murder, and other charges in connection with the shooting at Oxford High School on Tuesday, which killed four pupils and injured seven more.

On Monday, Oakland County Sheriff Michael Bouchard told Brianna Keilar on CNN’s “New Day” that “a teacher in the classroom where he was a student saw and heard something that she believed was concerning.”

He said, “And they had a counseling session with school authorities about it, and a phone call was left with the parents.”

Then, on Tuesday, “a different teacher in a different classroom saw some behavior that they felt was concerning, and they brought the child down to an office, had a meeting with school officials, called in the parents, and ultimately it was determined that he could go back into class,” according to the report.

Crumbley allegedly opened fire outside a school bathroom shortly after, according to authorities. Prosecutors said he moved through a hallway at a “methodical pace,” shooting students in hallways and classrooms before surrendering in the deadliest school shooting in the United States since 2018, and the 32nd since August 1. Bouchard would not say what the teachers’ concerns were, but he did say that his department was “never aware of any meeting previous to the incident or that there were any concerns about conduct.”

“It will all be part of the inquiry, in terms of what they believed, and why they thought that was the proper approach,” Bouchard said when asked why Crumbley was allowed to return to class on Tuesday.