Authorities in Oakland County, Michigan say a 15-year-old sophomore opened fire at his Michigan high school on Tuesday, killing three students. He shot and wounded six other people, including a teacher, the Associated Press reports.

The shooter’s motives are not yet known.

“Officers responded at around 12:55 p.m. to a flood of 911 calls about an active shooter,” at Oxford High School, according to AP News. “Authorities arrested the suspect at the school and recovered a semi-automatic handgun and several clips,” the outlet reports.

Superintendent Tim Throne said he was “shocked” by the incident. He did not know the names of the suspect or victims.

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As per AP, “The school was placed on lockdown after the attack, with some children sheltering in locked classrooms while officers searched the premises. They were later taken to a nearby Meijer grocery store to be picked up by their parents.”

The school is in Oxford Township, a community of about 22,000 people about 30 miles north of Detroit.

The local LakePoint Community Church is holding a prayer vigil at 7 pm Tuesday night (Nov 30) for the victims.

This story is still developing.