Its only one factor, so I wouldnt want to overstate the point. Other factors may include a variety of pressures others have mentioned in recent posts, a claustrophobic suffocating form of community, excessive moral or religious double-think, uptight refusal to look at issues, eg of parent-child relationships on a less superficial level. Plus the geography of the nation (eg isolated communities), a variety of authoritarian tendencies in wider society and state organs, oversubscription of inappropriate psychiatric drugs and a 'quick fix pop a pill for that' attitude, a failure to make the most of certain forms of humour as a self-preserving lifeline, immature idealisation that reality cannot live up to, the superficial disconnected form that gun-related violence takes as opposed to more physical forms of violence. I'm even tempted to include the higher age limits for drinking alcohol as a small part of the mix, when considering isolated youth who lack other outlets for their frustrations. And if Im going to go that far I may as well thrown caffeine in there.
Obviously there are economic and political factors at work too, though I'm not dwelling on those so much in this particular case because of how young the perpetrator was, and other apparent demographic features of this case.
Some of my above points can be tested by considering what factors the UK has in common with the USA, and which ones are different. Obviously the largest practical difference is in terms of gun culture & politics, but in some other regards we may be closer to the USA than many parts of Europe when it comes to certain economic, media, violence and explosive mental meltdown factors. But our coping strategies vary, more likely to find rivers of vomit here than rivers of blood.