By Amir Vera and Taylor Romine, CNN
(CNN) -- A 15-year-old boy is in custody after three students died and eight were injured in a shooting Tuesday afternoon at a high school in Oxford, Michigan, authorities said.
The Oxford High School students killed were a 16-year-old boy, a 14-year-old girl and a 17-year-old girl, Oakland County Undersheriff Michael G. McCabe said at a news conference.
Eight others were shot, one of whom is believed to be a teacher, McCabe said. Of the eight injured, two are currently in surgery and the other six are in stable condition with various gunshot wounds, McCabe said.
"I think this is every parent's worst nightmare," said Gov. Gretchen Whitmer, who added that shootings at schools are "a uniquely American problem that we need to address."
"My heart goes out to the families, this is an unimaginable tragedy. 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," Whitmer said.
The 15-year-old suspect, a sophomore at the school, was taken into custody without incident five minutes after authorities responded to the shooting, McCabe said. His parents have hired an attorney and have not permitted that he talk to police, McCabe said.
How the shooting unfolded
McCabe said calls for an active shooter came in around 12:51 p.m. ET. Oxford is about 45 miles north of Detroit.
"We received over 100 911 calls to our dispatch center," McCabe said.
A handgun was recovered from the suspect, McCabe said. Authorities recovered multiple shell casings in the school and believe around 15-to-20 shots were fired. There is no indication the suspect was wearing body armor, McCabe said.
"At this point in time, we believe he acted alone," McCabe said. He said that authorities are aware of how the suspect allegedly got the gun into the school, but declined to divulge those details.
All evacuated students were relocated to a nearby store for reunification with relatives. About 25 agencies and close to 60 ambulances responded, according to John Lyman, public information officer for the Rochester Hills Fire Department.
The families of the victims have been notified. It is not currently known if the three students killed were targeted, McCabe said.
"We've done three sweeps of the high school to make sure there's no other victims," he said. "We don't have a motive at this point in time, we are still investigating that."
A search warrant has been executed at the suspect's home, McCabe said.
McCabe said the suspect could be charged as an adult, but that is up to the Oakland County Prosecutors office. CNN has reached out to the Oakland County Prosecutors office for comment.
Oxford Community School officials released a statement confirming the shooting and saying the "Oakland County Sheriff's Department has secured the scene."
"Oxford High School students and staff are systematically being evacuated to the Meijer Garden Center and may be picked up there. Any students with their own transportation have been allowed to leave. All other district schools are in lockdown for safety purposes and are in no danger," read the statement, which was obtained by CNN affiliate WDIV.
Oxford Community School Superintendent Tim Throne said during the news conference the shooting left him shocked. "It's devastating," he said.
Throne declined to say why there were no metal detectors in the school, but did say -- to his knowledge -- metal detectors never came up in conversation prior to the shooting.
President and state officials react to shooting
President Joe Biden addressed the shooting Tuesday while in Minnesota, saying "my heart goes out to the families enduring the unimaginable grief of losing a loved one."
"You've gotta know that that whole community has to be in a state of shock right now," Biden said.
Michigan Attorney General Dana Nessel said her department has offered assistance to local law enforcement and that she has extended her "sincere gratitude," to the first responders on the scene.
"My heart goes out to the parents who have lost their children and to the students, teachers, staff, and families reeling from the tragedy of a school shooting within their community," Nessel said. "We must act to properly address gun violence in our schools and the ongoing threat of another unconscionable tragedy if we continue to only offer thoughts and prayers. Our kids deserve better."