We're going to turn to new details on the middle school shooting in nevada, including what may have triggered the incident and where the boy got his gun. Abc's cecilia vega has the story. I'm calling... See More
We're going to turn to new details on the middle school shooting in nevada, including what may have triggered the incident and where the boy got his gun. Abc's cecilia vega has the story. I'm calling from sparks middle school. We have a shooting at our school. Reporter: That gunman, police now says was a 12-year-old boy. A seventh grader. And that gun, a 9 millimeter ruger handgun, similar to this. We believe that the student got it from his residence. We some kids outside who had a gun pointed at them. So, we have lockdown. Reporter:911 shows how the boy terrorized the schoolyard outside of reno, nevada, just minutes before the morning bell rang. Somebody brought a gun to school that shot a teacher. The teacher's down? Yes. Reporter: This morning, the memorial for mr. Michael landsberry, continues to grow. The vet who served twice in afghanistan, turned math teacher, killed as he tried to stop the shooting. I cannot express my -- enough appreciation for mr. Landsberry. He truly is a hero. Reporter: Two other boys, shot before the gunman killed himself, expected to survive. And now, police are looking into whether the boy shooter's parents might be criminally responsible. Did they knowingly permit their child to have access to this weapon? If there's enough circumstantial evidence, then it's entirely likely they could charge the parents criminal. Reporter: Was this young killer targeting specific people? Police say they don't know. Students here tell me he was bullied. But clearly, he was very angry when he opened fire on the schoolyard. We still don't know his name. Police say they may never reveal it, out of respect for his grieving family. A lot of questions still to run down. That's right.
This transcript has been automatically generated and may not be 100% accurate.