To be honest, I do not know who did it. While I am inclined to think it was jihadis backed by Saudi cash the fact that it was done somewhat competently makes me reserve a tiny bit of reasonable doubt that it actually could have been done by a right wing group, as they tend to actually accomplish what they set out to do.
But what I think is actually much more important than who did it, is who is happy about it. I have been searching for clips of muslims dancing in the streets and passing out sweets, an indicator much more of what ideology is deleterious than merely who did this heinous act. So far, the clips I have seen have been of questionable origin. The one going around the most looks to me like a muslim wedding in some small town and is being misrepresented as dancing Muslims over this attack. This is very unfortunate for all of us.
But this is revealing. Thank you Magic Martin.