Didn't al-Qaeda take credit for this?
Yes, and bin Laden's objective has always been to foment independent actions just like this. There's undoubtedly an ideological connection, and that's good enough for me. The left is still obsessed with the idea of combating Islamist terrorism with police instead of military. They rationalize that the number of deaths western societies are taking are insignificant, and that Islamists are reasonable people who would never employ the weapons of mass destruction they don't have and will never obtain. The left is setting the west up for a massive Darwin Award.