A 15-year-old student allegedly opened fire at a high school in rural Michigan on Tuesday, killing three other students before being taken into custody, police said.
Six others, including one teacher, were wounded in the attack, which took place shortly after noon at Oxford High School, the Oakland County Sheriff's Office said in a statement.
A second-year student was taken into custody and a handgun was seized, but there was no immediate explanation for what prompted the attack in Oxford, a small town about 40 miles (65 kilometers) north of Detroit.
"There was no resistance during the arrest and the suspect has asked for a lawyer and has not made any statements as to a motive," the sheriff's office said.
"It's a very tragic situation," Undersheriff Michael McCabe told reporters.
"We have three deceased victims right now, who are all believed to be students," he said.
"We have lots of upset parents," he said.
Police said they received more than 100 911 emergency calls shortly after noon, and that the shooter unleashed 15-20 shots over about five minutes from a semi-automatic handgun with more than one magazine.
The suspect was taken into custody within five minutes of the first 911 call, they said.
President Joe Biden was informed of the shooting during a visit to Minnesota.
"My heart goes out to the families enduring the unimaginable grief," he said.
"You know, that whole community has to be just in a state of shock right now."
Elissa Slotkin, who represents the district north of Detroit in the US House of Representatives, said she was "horrified" by the shooting.
"I've been talking with Oxford leaders, parents and students and we are all praying for the health of those injured, and the well-being of all our young people, many of whom are in shock," she said in a statement.
- Deadliest school shooting in 2021 -
It was the deadliest school shooting so far this year, according to Everytown For Gun Safety, a group which keeps statistics of mass shootings and lobbies for gun control.
Before Tuesday's incident, there had been 138 shootings in schools across the United States in 2021, according to figures provided by Everytown. In those incidents, 26 resulted in fatalities, though no more than two each time.
The deadliest school shootings in US history were the April 2007 attack at Virginia Tech in Blacksburg, Virginia, which saw 33 killed, including the shooter, followed by the December 2012 attack on the Sandy Hook elementary school in Newtown, Connecticut, which left 28 dead, including 20 children and the shooter.
In February 2018, a former student with an AR-15 assault rifle opened fire in his former high school in Parkland, Florida, killing 17, in the deadliest-ever high school shooting.