A motive for the shooting remains unknown, but the attack was planned in advance. State Police Chief Pete Kassetas said some students were warned by the suspect against coming to school.
It was a typical morning at Berrendo Middle School on Tuesday, with students gathering at the gym before classes to escape the cold.
Then shots rang out, and students saw a fellow student bleeding on the floor with a gunshot wound to the face.
"I just saw blood everywhere," Essance Sosa, 12, said. "Everyone started screaming and running."
Within 10 seconds, the suspect, a seventh grader at the school, had shot an 11-year-old boy in the face and a 13-year-old girl in the shoulder.
Authorities say John Masterson, an eighth-grade social studies teacher, immediately stepped in and talked the boy into dropping his weapon.
"He stood there and allowed the gun to be pointed right at him," Gov. Susana Martinez said at a prayer vigil Tuesday night, "so there would be no more young kids hurt."
Masterson held him until authorities arrived.
The male victim remains in critical condition after undergoing two surgeries.The female victim, identified by the governor as Kendal Sanders, is in stable condition. The police chief said it appears that the victims were chosen randomly.
The suspect was transferred to an Albuquerque psychiatric hospital after a hearing Tuesday. He has not yet been formally charged. The family of the suspect is expected to release a statement Wednesday.
According to the police chief, the suspect got the shotgun from his family's home and had three rounds of ammunition.
The Associated Press contributed to this report.