Students at a New Mexico high school hid in their classrooms as a gunman opened fire and killed two classmates before also being found dead.
Authorities and other officials in the small town of Aztec, near the Colorado border, have released few details other than to say the gunman and the two victims all attended Aztec High School.
No other injuries were reported, and it was not clear if the gunman died by suicide or was killed by police.
Local and federal authorities are investigating what led to the shooting and did not immediately release any details about the circumstances. A news conference was planned later.
Sophomore Garrett Parker told Albuquerque television station KOAT he was upstairs in history class when he heard what he initially thought was students banging on lockers.
As the noise got louder and closer, school officials issued a warning over the loud speaker.
"Thankfully our teacher always locks the door no matter what. So he kept that locked," he said.
"When they called over the intercom that it was not a drill, we went to the corner of the room out of sight from the door and just started hiding."
He said it felt like a dream.
Some parents reported hearing from their children via text messages that they could hear the gunman approaching.
The school of about 900 students was cordoned off as authorities cleared the campus and teenagers were taken to another location where they could be reunited with their parents.
A crowd of nervous parents initially gathered outside City Hall to wait for more information as officers tried to reassure them about the safety of their children.
All schools in town closed for the day, but authorities said there were no other credible threats to students at the high school or other schools in the neighbouring communities of Bloomfield or Farmington.
Aztec is a rural community of 6,500 people in the heart of northwestern New Mexico's oil and gas country and near the Navajo Nation. Its main street is lined by old brick buildings that date back more than a century.
Residents voiced disbelief on social media, while members of the New Mexico congressional delegation, state Attorney General Hector Balderas and other elected officials offered their condolences and other assistance.
US Rep. Ben Ray Lujan said on Twitter: "While details are still coming in, we grieve for the innocent victims in this senseless act of violence. Too many lives have been disrupted and too many futures cut short."
My heart breaks for the victims & families of the tragic shooting at Aztec HS today. While details are still coming in, we grieve for the innocent victims in this senseless act of violence. Too many lives have been disrupted and too many futures cut short.— Ben Ray Lujan (@repbenraylujan) December 7, 2017