No matter who it was, it is an act of terror.
I tend to think that whoever it was was likely "home grown" and given the number of bombs, and
the coordination involved, it was more than one person.
The thing that I hate most of all is that the people that did this achieved their aim, because world wide,
this is going to change how things are done, and people looking over their shoulders takes away from
whatever event they are attending.