> No group has stepped forward to claim the attack- half the "fun" of a terrorist organization is spreading fear through your message.
I don't have any reason to think this was a terrorist attack, but I have the impression that (credibly) claiming responsibility for attacks is less common than it used to be. The Mumbai attacks last year, for example, were just miscellaneous mystery terror.
I agree with you, but to use your Mumbai attack example, "everyone" (everyone I've read) basically believes that the Pakistan CIA-equivalent helped sponsor the attacks. An organization taking responsibility for the attack would lead back to this organization, which would involve a lot of political drama.
As long as Pakistan doesn't openly claim responsibility, there's no real loss in political capital to them- Indians hate them anyway, and any time an attack happens, India seems to rattle its sabers for a few months before backing down and they remember that Pakistan is also nuclear capable.
I don't have any reason to think this was a terrorist attack, but I have the impression that (credibly) claiming responsibility for attacks is less common than it used to be. The Mumbai attacks last year, for example, were just miscellaneous mystery terror.