regardless of who did this crime, the fact is it was a mostly successful operation or act if the desired effect was to kill, scare, create chaos and raise suspicion on almost every one.
the person who did this could be black, white, brown almost anyone can make a bomb from components found easily and described on the internet and print books.
there are plenty of white muslims and am sure there are white muslim extremists as well. and the worst part is there are seemingly no rules to what they will do or who they will kill, if other muslims get killed it the bombing they are considered small price to pay for there cause.
so the big question is how long till the streets are filled with checkpoints and metal detectors? not that they will help for long as non metallic weapons and hard to detect bombs are now a reality.