Terrorist attack in Boston

[Lemonray]

My teacher today had an interesting thought; what if it was North Korea?
I can see where he's coming from but I don't think that they would do something this 'small' given the threats in the past few months.

It's not outside the realm of possibility, but NK being behind an attack such as this isn't all that likely.

Realistically, it's much more likely that a domestic terrorist (multiple domestic terrorists?) or jihadis are behind it. This particular attack seems more like something a domestic terrorist would do, but who knows.