This was always ever increasingly likely as ISIS and wannabe ISIS attack the west. Unfortunately there are enough members of society unwilling to think things through. EDL and the like have always been a bit of a joke but with the increase in attacks from Islam identifying people I worry this country will see the rise of some proper right wing groups like that of in the US.
In this case: if it's politically motivated it's terrorism, if it's not it could be an emotional revenge attack which would be simple murder. Apparently he said he wants to kill all muslims though so I think that falls under politically motivated. I know why the media will call it a right wing attack, but I think that's missing the mark - right wing suggests nationalism/racial dominance in the extreme, this is a case where the individual is revenge attacking a particular demographic, within which is a group that is attacking his people/country. If he equally wanted all immigrations of different ethnicities deported you could call him right wing. Obviously it'd do nobody any favours for the media to point this out but in assessing it, this is the case I feel - acting upon one of the most basic of human instincts.