I don't believe this was an Islamist attack either. A letter was left behind near the bus, but no video was released. Islamist usually don't leave letters behind, they claim their responsibility via video. The letter was written solely in German. The design of the bombs was extremely professional(directed blast, metal bolts, 3 linked devices, remotely fired), but the explosive mass was very, very little(only ~200g TNT equivalent). Islamists' devices are usually very amateuris