Yeah, I'm not happy it turned out that way either, nor would I have been happy had it turned out to be a right wing nutjob. These killings are troubling, and not just because they are killings, though that is bad enough, but because they are also political in some way. Politically motivated killings have bad consequences which ripple out in society. For example, this kind of thing may motivate other radical Muslims to take similar action, and it will also undoubtedly cause the peaceful ones to face some resentment and discrimination, or even violence.
One thing is certain, we are facing a rather intense wave of mass killings in this country right now, and they seem to stem from a variety of different or even disparate motives. I don't have any solutions but would advise anyone against making any presumptions based on how they view the world beforehand because such presumptions may or may not serve them well.