OAKLAND COUNTY, Mich. — A 15-year-old sophomore opened fire at his Michigan high school on Tuesday, killing three students and wounding eight other people, including a teacher, authorities said.

The three students killed were a 16-year-old male, a 14-year-old female and a 17-year-old female. Police said two people are currently in surgery for their injuries and the other six are in stable condition. A deputy has been assigned to each of the families.

The student was in class on Tuesday prior to the shooting, police said.

Oakland County Undersheriff Mike McCabe said at a news conference that he didn’t know what the assailant’s motives were for the attack at Oxford High School in Oxford Township, a community of about 22,000 people roughly 30 miles north of Detroit.

Officers responded at around 12:55 p.m. to a flood of 911 calls about an active shooter at the school, McCabe said. Authorities arrested the suspect at the school and recovered a semi-automatic handgun and several clips.

Police say they were unaware of any warning signs and it is unknown if the victims were targeted.

“Deputies confronted him, he had the weapon on him, they took him into custody,” McCabe said, declining to share more detail about the arrest.

Authorities didn’t immediately release the names of the suspect or victims.

Tim Throne, the superintendent of Oxford Community Schools, said he didn’t know yet know the victims’ names or whether their families had been contacted.

“I’m shocked. It’s devastating,” the shaken superintendent told reporters.

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.

McCabe said investigators would be looking through social media posts for any evidence of a possible motive.

Robin Redding, the parent of a 12th-grader, told The Associated Press that there had been rumblings of trouble at the school.

“He was not in school today. He just said that ‘Ma I don’t feel comfortable. None of the kids that we go to school with are going today,’” Redding said.

Authorities say they’ve reached out to the parents of the shooter, who did not want to speak and are getting an attorney.

“I hope we can all rise to the occasion and wrap our arms around the families, the affected children and school personnel, and this community,” said Michigan Gov. Gretchen Whitmer through tears at the 5 p.m. press conference.

“This is a uniquely American problem that we need to address,” she said. “But I think it’s too early to talk about policies that might need to change as a result of this. At this point, we need to focus on the tragedy at hand.”

More information is expected to come at a press conference at 10 p.m. EST.