Transcript for Knife-Wielding Student Shot by Officer at Nevada High School

Now to a dramatic school shooting caught on camera. A campus police officer in Reno, Nevada, firing on a knife-wielding student and ABC's T.J. Holmes has more on these terrifying moments. Good morning. Reporter: Incredibly we saw the video of this incident almost immediately after it happened. A kid wildly swinging a knife in the middle of the school day in the middle of the school yard before being shot and as you'll see in the video many instead of running, what did they do, pulled out their phones and started recording. This 14-year-old student seen on camera wildly swinging at least one large knife is in critical condition this morning shot by police trying to stop him. Shots fired with a student down at hug high school. Reporter: It started as a fight between two students at this Reno high school around lunchtime. Back off. Back off. Reporter: It quickly escalated when the 14-year-old boy pulls the knife in the middle of a crowd but the student refuses to drop the knife. The officer fires a single shot. He's going around telling everybody he's going to shoot and stop everybody so I mean he finally did it and he got stopped. The officer gave verbal commands for the student to drop the knife, ultimately firing his service weapon stopping the threat. Once the threat was stopped, the shooting officer immediately began to provide medical aid to the student. Reporter: The teen is critically injured on the group as the school is put on code red lockdown. Officers are going classroom to classroom looking for potential other victims, looking for witnesses to the incident to make sure the kids are safe. Reporter: No one else was injured and detectives now interviewing witnesses and asking for any other videos like these. The officer is now on paid leave. As you can see in that, middle in the school day, middle of the school yard kidding standing around recording it. You might think kids take off and run but these days they have these phones and now it will be an important investigative tool asking for all those videos. Hard to see how the officer had that much choice. You got so many potential victims. You do. All right, T.J. We'll move on to Charleston, South Carolina, where dylann roof is on trial for killing

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