The 9mm Sig Sauer used to kill 3 people and wound eight others at a Michigan high was bought by the 15-year-old suspect’s dad on Nov. 26, authorities say.

Oakland County Sheriff Michael Bouchard said late Tuesday that the suspect had practiced shooting with the gun and posted pictures of it and the target. Bouchard said he did not know why the boy's father bought the gun.

Bouchard said several students from the shooting remain in critical condition, including 14-year-old on ventilator.

Authorities have said they are still trying to determine a motive for the shooting at Oxford High School in Oxford Township.

THIS IS A BREAKING NEWS UPDATE. AP’s earlier story follows below.

OXFORD TOWNSHIP, Mich. (AP) - A 15-year-old sophomore opened fire at his Michigan high school on Tuesday, killing three students and wounding eight other people, including one teacher, authorities said.

Oakland County Undersheriff Mike McCabe said at a news conference that investigators were still trying to determine a motive for the shooting at Oxford High School in Oxford Township, a community of about 22,000 people roughly 30 miles (48 kilometers) north of Detroit.

McCabe said he was aware of allegations circulating on social media that there had been threats of a shooting at the roughly 1,700-student school before Tuesday's attack, but he cautioned against believing that narrative until investigators can look into it.

He also downplayed the significance of an incident in early November when a deer head was thrown off the school roof, which he said was “absolutely unrelated” to the shooting. The vandalism prompted school administrators to post two letters to parents on the school’s website this month, saying they were responding to rumors of a threat against the school but had found none.

Authorities didn't immediately release the suspect's name, but McCabe said deputies arrested him within minutes of arriving at the school in response to a flood of 911 calls about the attack, which happened shortly before 1 p.m. He said the deputies also recovered the semi-automatic handgun and several magazines used to store ammunition that the suspect used in the attack.

“He fired multiple shots,” McCabe said. “Somewhere in the area of 15 to 20.”

The three students who were killed were a 16-year-old boy and two girls, ages 14 and 17, McCabe said. Two of the wounded were undergoing surgery as of 5 p.m. and the six others who were wounded were in stable condition, he said.

McCabe said the suspect's parents visited their son where he's being held and advised him not to talk to investigators, as is his right. Police must seek permission from a juvenile suspect's parents or guardian to speak with them, he added.

Oakland County Prosecutor Karen McDonald issued a statement Tuesday evening saying her office expects to issue charges quickly and that an update would be given Wednesday.

McCabe said he wasn't aware of any prior run-ins the suspect had with law enforcement or if he had any disciplinary history at school.

Gov. Gretchen Whitmer also spoke at the news conference, saying, “I think this is every parent’s worst nightmare,” while choking up.

President Joe Biden, before delivering remarks at a community college in Rosemount, Minnesota, said: "As we learn the full details, my heart goes out to the families enduring the unimaginable grief of losing a loved one."

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 district said in a statement that all of its schools would be closed for the rest of the week.

Isabel Flores, a 15-year-old ninth grader, told WJBK-TV that she and other students heard gunshots and saw another student bleeding from the face. They then ran from the area through the rear of the school, she said.

McCabe said investigators would pore over the school's video footage and look through social media posts for any evidence of a possible motive.

A concerned parent, Robin Redding, said her son, Treshan Bryant, is a 12th grader at the school but stayed home Tuesday. She said he had heard threats that there could be a shooting.

“This couldn’t be just random,” she said.

Redding didn’t provide specifics about what her son had heard, but she expressed concern with school safety in general.

“Kids just, like they’re just mad at each other at this school,” she said.

Bryant said he texted several younger cousins in the morning and they said they didn’t want to go to school, and he got a bad feeling. He asked his mom if he could do his assignments online.

Bryant said he had heard vague threats “for a long time now” about plans for a shooting.

“You’re not supposed to play about that,” he said of the threats. “This is real life.”

At a vigil at Lakepoint Community Church on Tuesday night, Leeann Dersa choked back tears as she hugged friends and neighbors. Dersa has lived nearly all of her 73 years in Oxford and her grandchildren attended the high school.

“Scared us all something terrible. It's awful,” Dersa said of the shooting. “We’ve had some tragedies with the young people dying through the years, and we’ve all come together and all helped each other and we’re still coming together with them and love them.”

For Greg Hill, the day twisted his stomach in knots. His children attend the elementary school in the district, and he brought them to the vigil.

“Just glad that our children are safe and now it’s time for the community to heal,” Hill, 40, said.

Pastor Jesse Holt said news of the shooting flooded in to him and his wife, including texts from some of the 20 to 25 students who are among the 400-member congregation.

“Some were very scared, hiding under their desks and texting us, ‘We’re safe, we’re OK. We heard gunshots, but we’re OK.’ They were trying to calm us, at least that’s how it felt,” he said Tuesday night.

One student texted that she was hiding in a bathroom with a boy who also was seeking shelter.

After deputies arrested the shooter, the girl ran from the school and was taken in by someone living close by until her mom could pick her up, Holt said.

“That’s our community,” he said. “That’s who we are.”