No offense, but I'm not sure that you read or understood the whole article. It said that the boy who was shot in the neck (not the head) was the victim and that the resource officer apprehended the suspect, not that he shot him. It then goes on later to say that the incident was likely due to an ongoing altercation between the two students. It sounds like there was only one shot fired at one student and the suspect left, only to be apprehended a few minutes later by the officer.
I'm glad that it was not some sort of massacre and definitely agree that cases exist and out there and should be spread where armed guards/citizens stop a threat before more damage is done. However, it appears that this particular case does not actually fit that criteria for our purposes.