"When someone like that performs an extreme act it's because they've misread the social signals of others"
Or, and I would say more likely, it's because they are evil and/or unhinged. The reactions to this incident, from various factions, I've found interesting; the far right commentators immediately panicked, for example, the instant they heard of a (incorrect, it seems) connection with Britain First. Doubtless, had the man been a member - not likely as there are very few - it would be difficult to confirm it now. The opposite pack immediately marched in with their own agendas, highlighting the connection with extremism. The tabloids, and others, immediately applied the Terrorism tag to the murder, without any real evidence. This was the brutal and needless killing of a well-liked and respected, hard-working woman, who did nobody any harm, by an idiot, a murderer, a worthless human being. Nothing more, and nothing less.