Unless some different information comes out, I wouldn't even call this "violence". And it could have happened anywhere if they were friends. School just happens to be a place they spend a lot of time.
But it did happen in a school, and schools are gun-free zones under the law.
So much for laws making us safe.
As to the violence, I agree with you. Under a dictionary definition, I will concede that getting shot and dying is a violent way to go. But an accidental/negligent shooting, one in which even the prosecutor has publicly acknowledged that there was no intent, is not what the general populace regards as "gun violence." But the anti-gun forces can be counted on to seize upon any and every such incident to build up their statistics proving that "gun violence" is a major problem.
The issue, of course, is that their proposed solutions always involve enacting more laws. What's the point if/when the laws already on the books failed to prevent an incident? How many existing laws were broken by this kid's bringing a loaded handgun into a public school? First, obviously, he brought a loaded gun into a gun-free zone. Was it his gun? He's sixteen years old, which I think means he can't legally own or possess a handgun. (Not sure on that.) If if was a parent's handgun, then he stole it in order to bring it to school. How did he get to school that day? Does Texas allow unlicensed carry of loaded handguns? By minors? And if he rode a school bus, there's probably a state law prohibiting the carry of firearms on public transportation. I'm sure a good lawyer could probably dredge up several more laws that were broken.
But the incident happened, in spite of all the laws that should have prevented it. Obviously, then, we need another law that makes doing illegal things more illegal.