I do agree, that it is very possible to reduce the number of guns around and that then it is also harder for criminals to get one.

But as far as I know, now it is also pretty much illegal to carry a knive around in the UK, as the crime with knives were and are very high (but still lower than the US).

But in general I do not agree to the idea to reduce the problem to the number of guns. Germany for example has a quite high number of guns per capita (higher than one would expect) and so has switzerland, but both have lower homicide rates than the UK.

I would rather focus on the reasons, why someone goes homicidal.