The problem surely will always be 'Well how do you measure the level of someones stability'?   The guy who perpetrated this shooting, walked into a gun shop a short while ago and bought his handgun...a simple sale.....possibly having already meditated over his possible future behaviour. I am sure the problem goes a lot deeper than that when it gets down to 'the rights of the people'.
The UK is fast becoming an illegal gun culture so how long will it be before we can rightfully bear arms? If only for our own protection.
Sad to say IMHO it is just another sign of the breakdown in our societies. Best wishes, Mike.