I don't think any gun control would stop these kind of things... they'll just find a different weapon.
My thoughts and prayers are with the victims.
Do you really think he could have knifed 27 people to death? I guess he could have used a crossbow, but that's about it...
I'm support gun control, but the truth are that massacre like this, could still happen. Yes with gun control we would likely not see the standard school shooting where a students shoot other students. But when the killer is a adult, gun control doesn't help a lot (as we can see in the similar cases in Germany). Even in Denmark a country with gun control, I could get access to firearms if I really wanted to. It wouldn't be as easy as in USA and I would need money, but I could get them. Alternative I could make a bomb, again while it demands time and money it would be quite possible.
So this is case is an bad argument for gun control.