Of course it was revenge, revenge against a people group based on religion, due to others of the same religion attacking this guys "own" people group. Not hard to see that. Sure it is simple murder, sure it is crazy but that doesn't mean it isn't being done as "revenge" in that persons mind.
Was the attack on innocent people in Manchester and London Bridge not "revenge" by certain people against a certain culture? Of course it was in their mind, that's why they are doing it. It is simple murder then too and it is crazy.
Just because something is murder and crazy doesn't invalidate it being done in the name of revenge.
All in cases we have seen, innocents are the ones being targeted, people who have nothing to do with either side of the issue.