I think at this time our thoughts are firstly with the victim and his family.
While it is too soon to know exactly what happened and why - I suspect that they are doppelgangers
of Norwegian fascist mass murderer Anders Breivik. These extremists are all the same - ignorant, selfish, vain, cowardly bigots and should be treated with the contempt that they deserve.
I think the best way to respond is to click here and donate whatever you can to "Help for Heroes" http://www.helpforheroes.org.uk/donate/. Pass this on.