I don't like it when the "other side" responds to a terrorist attack with smug glee when they think it confirms their pet prejudices, and I'm rather hoping that "my side" can refrain from the same when thinking that this attack confirms ours.
If I had to guess, I'd say that whoever the perpetrator was, they were probably acting alone - there were only two bombs, and they went off nearly thirty minutes apart. I think the bombings themselves are connected, in that they were both planted by the same perpetrator, but whoever that perpetrator was did this all by himself. They don't appear to be sophisticated devices from the description, and the way the bombs went off and their short distance from each other (maybe a mile and a half, per the map
here) suggests to me that one person cobbled them together, planted one, then went and planted the other without the use of any kind of elaborate timing mechanism or bomb design. I'm pretty sure, at this point, it wasn't any kind of organized PEGIDA strike or whatever, despite the speculations based on Dresden's history with that group.
Of course, I could be totally wrong about all of this. I'm just glad no one was killed or even apparently hurt this time, and I hope whoever did this is caught soon.