I'm just thinking about the guy that has done this. From the photo issued in the press, the one of him sitting on the bench, I would say that he 'doesn't look quite right' and that was the first thing that struck me when I saw him, by that I mean I think he may have a mental health issue. He's a long term volunteer so that puts him on benefits, most likely ESA or similar. He appears to be fully active and physically fit therefore it's quite possible that his need for benefits points to the fact that he does indeed have some kind of mental health issue. Now mix this with being brainwashed (easily led too perhaps) and we have the ingredients for something like this.
I am speculating of course, but I think it's a reasonable speculation (if there's such a thing) and what this gives us is more of what myself/Freakbro touched on (we didn't actually touch, honest!) earlier and makes it all very complicated with all sorts of possible theories, claims, defences, allegations, pleas, outcomes etc.