I'm neutral on gun lesislation but the volo logic reads like this.
Upstanding citizens should have access to guns.
Criminals shouldn't, but will get them via criminal means.
Spree killers arn't upstanding citizens, but arn't criminals either, so where are their guns coming from.
Answer is, the same place as the guns of upstanding citzens, either bought themselves or from friends/relatives.
Which means, logically, that if upstanding citizens didn't have access to guns, then neither would spree killers unless they resorted to criminal means.
There are lots of arguments against gun legislation, but this is not one of them.
Just saying.