Students hid in their classrooms, some behind locked doors or in closets, as a gunman opened fire on Thursday inside a New Mexico high school, killing two classmates before he ended up dead.
Authorities and other officials in the small town of Aztec near the Colorado border have released few details other than to say the shooter and two victims attended Aztec High School.
No other injuries were reported, and it was not clear if the shooter died by suicide or was killed by police.
Bryn Divine, a senior, said she was sitting at her desk in her history class when she heard gunshots erupt down the hall. At first, it sounded as if someone was swinging a metal baseball bat against the lockers.
Then she heard an announcer over the school intercom tell students: "This is not a drill."
"I stayed in my desk, and I just prayed, 'Please just let this be over as soon as possible.' That was my first reaction," she said.
Sophomore Garrett Parker told Albuquerque television station KOAT that he also heard what he thought was banging on the lockers. Then it got louder and closer.
"Thankfully our teacher always locks the door no matter what. So he kept that locked," Parker 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."
Gov. Susana Martinez called the shooting a heinous and horrific act and told reporters that teachers, school staff and law enforcement jumped in quickly to prevent more deaths. She didn't provide more details.
Police responded to the school less than a minute after getting the initial calls, which came shortly after the start of the first period. With the school in lockdown, they got inside through a window and a door.
Authorities checked each room and each building at the school before the students were bused to another location where they were reunited with their parents.
The high school remained cordoned off as the community prepared for a prayer vigil on Thursday night. Aztec is a rural town 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.
Local, state and federal authorities said at a news conference that they had a lot of evidence to process and many interviews to conduct. They also were asking any students who might have seen something to call police.
School Superintendent Kirk Carpenter choked up, describing it as a tough day.
"At schools, our primary role and our primary job is to educate students and keep them safe, and when you have something like this, it hits you in the heart," he said.
Aztec school officials say schools across town that shut down Thursday will likely stay closed Friday.
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.