1) I asked who did it.
Got Page of Cups card.
This suggests it was carried by someone who did it as a service to another. He is loyal to an individual or a cause.
2) Motive of the mastermind (according to 1st card, this would be a different individual. We already know motive of the one who carried it out)
Two of Wands- dominant personality, attainment of goals, ruler, bold, melancholy in the midst of worldly riches
This is someone who is wealthy and in a leadership position who wants more power. Wealth is not enough for him.
This answer doesn't surprise me, as my first intuition when I heard about the bombing was that we will never know the whole story.