I don’t know. As someone interested in soccer who also is very concerned about terrorism, I ought to know, but so far haven’t heard anything yet. Nor can I think of a reason why Dortmund in particular was attacked. Attacking a soccer team in Europe is attacking European culture, but any team could have been attacked. Why Dortmund, then? Like I said, I don’t know. It’s always possible it was not Islamic terrorism and was merely done by a fan of a bitter rival.