A sixth-grader opened fire at a private school in the northern Mexican state of Coahuila, killing his teacher and injuring six others before taking his own life, CNN reports.

Coahuila Gov. Miguel Angel Riquelme told reporters that the 11-year-old arrived at the school telling his classmates, “Today is the day.”

According to the governor, the student went to use the restroom at 8 a.m. After being gone for nearly 15 minutes, his teacher went to check in on him. When she found the boy, he was walking out of the restroom wearing a shirt that said “Natural Selection,” a reference to the first-person shooting video game, and holding two guns in his hands. 

After fatally shooting his teacher, the boy opened fire at classmates, injuring six, before directing the gun at himself.

“He had mentioned the video game, which I believe he tried to recreate today,” Riquelme said.

The mass shooting took place at the Cervantes de Torreón School in Torreón, an industrial city in Coahuila. The private school serves about 1,900 students from kindergarten through high school.

In a post on Facebook announcing the tragedy, school representatives expressed their surprise surrounding the fatal event that occurred.

“We never would have imagined that a situation like this could occur in our society,” the post read. 

School officials are currently working with law enforcement in their investigation into the mass shooting.