In the article it says he will get 21 years which is the maximum he can get under law, but that to be free again, he'd have to be deemed as no longer a danger to the public, and lawyers predict that would be insane and he will die in prison.
If he does all 21 years, he'll be 54 when he comes out. Which is not old enough for what he did. Hopefully he gets killed in prison. Most of the 77 were teenagers.