I think that Digwa's religion is irrelevant. He is clearly the kind of young man who is violent and would get his hands on some kind of blade regardless.
Responsible and law abiding gun owners lock up their weapons.
My ceremonial knives are stored safely, unlike my legal huge carving knives, cleavers, saws, hammers, etc.
As I have said before, people kill people, not a knife or a gun.
Or ropes, hammers, golf clubs, tights, chain saws, etc.
Shall we licence pillows, which can be used to smother people?
All the bans and restrictions on handguns, various blades, shotguns, whatever, will be observed by law abiding, non violent people and ignored by criminals and violent people, who will be able to obtain any weapon they want on the black market.
Hasty, knee jerk legislation is invariably bad law.
It would be better to concentrate on how we are socialising our NEET young people and being more discriminating about the people to whom we open our borders.