(USA TODAY) - Ten seconds of horror and one heroic teacher turned a normal New Mexico morning into one that will never be forgotten at a Roswell middle school that boasts of winning the girls city basketball championship and just days earlier issued its midyear report cards.

Police say a 12-year-old student walked into the gym shortly before school was to start Tuesday and began firing a sawed-off shotgun. Two students were wounded, one critically.

Authorities say John Masterson, an eighth-grade social studies teacher at Berrendo Middle School, saved lives when he immediately stepped in and talked the boy into dropping his weapon.

"The young man shoots and shoots and then is pointing the firearm at Mr. Masterson," Gov. Susana Martinez said. "Mr. Masterson then begins to talk to him, telling him to put it down. The Young man put it down and raised his hands."

"He stood there and allowed the gun to be pointed right at him so there would be no more young kids hurt," Martinez said.

Masterson then held him until a state police lieutenant dropping his own child off at the school was alerted to the shooting and took the shooter into custody.

"It was a harrowing experience," Masterson told the Albuquerque Journal. "All I can say was the staff there did a great job."

State Police Chief Pete Kassetas lauded State Police Lt. Gary Smith, the parent who was alerted by the school's principal that a shooting had just taken place.

"He left his son in the car and went to the gym," Kassetas said. "He had to make that difficult decision to leave his child and go into that school. Imagine having to make that decision."

Officials also credit previous "active shooter" drills by Roswell Independent School District for preparing teachers and students, who say they were ready for what happened Tuesday morning. Students say they even thought the shooting was a surprise drill at first.

"Our hearts and our prayers go out to the families and students who were affected by this senseless action," Superintendent of Schools Tom Burris said. He said the school would be closed Wednesday, but that plans were underway to reopen Thursday.

Investigators still aren't sure why the boy, who has not been named by authorities or formally charged, opened fire. Authorities said the boy sneaked the shotgun onto campus through a bag or musical instrument case.

An 11-year-old boy was critically injured and a 13-year-old girl was in stable condition.

The suspected shooter was transferred to an Albuquerque psychiatric hospital following a hearing Tuesday, according to attorney Robert Gorence, who is representing his family. Gorence said the family would release a statement Wednesday.

Officials at University Medical Center in Lubbock, Texas, said an 11-year-old boy was flown there in critical condition and a 13-year-old girl arrived in serious condition. The governor saidthe boy underwent a second surgery. She identified the girl as Kendal Sanders, 13, and said her condition was upgraded to stable.

Martinez said the family of the injured boy has asked that his name not be released while he recovers.