[LaunchedFireFly]

No matter what happens in the world, there will always be at least one person who wants to kill someone else. It doesn't really matter if the person is mentally ill or demented, if they want to kill they will try to find a way. They could use a gun. If you say to ban guns, then there are still many ways of obtaining one. They could either make it or get it on the black market. They could use a knife, now if you ban those, then society will be hurt because everyone uses knives. The point is that we don't live in a utopia. There is no real solution to end knife crime, there may be a way to lower the amount of events related to knife crime, but it won't be solved as long as people exist.
In short people are people and people act on what they feel is in their best interest.