Thats horribly sad. After watching the video, the only thing I can think is that they maybe should have better tethers. Even then, I do not know how this could have been avoided with cars like these. It is hard to keep the wheels on in an accident like that, the tire just got the kid perfect.
I feel horrible for his father. He came through the deadliest time in F1 to see it (and other series like it) become far safer, but then his son is taken away by it. Very sad.