"O Allah! Forgive our living and our dead, those who are with us and those who are absent, our young and our old, our men and our women. O Allah! Whomever you keep alive from us keep him alive on Islam, and whomever you take away from us, take him as a believer. O Allah! Do not leave us bereft of his good and do not send us astray after them."(Ibn Majah 1:480, Ahmad 2:368)
Ameen. The victims of the most recent attack here in Karachi are in my duas, may Allah(swt) give them peace and protect their families.
Some ayat for those responsible(and terrorists in general) to keep in mind-
5:32-On that account: We ordained for the Children of Israel that if any one slew a person - unless it be for murder or for spreading mischief in the land - it would be as if he slew the whole people: and if any one saved a life, it would be as if he saved the life of the whole people. Then although there came to them Our messengers with clear signs, yet, even after that, many of them continued to commit excesses in the land.
6:151-Say: "Come, I will rehearse what Allah hath (really) prohibited you from": Join not anything as equal with Him; be good to your parents; kill not your children on a plea of want;- We provide sustenance for you and for them;- come not nigh to shameful deeds. Whether open or secret; take not life, which Allah hath made sacred, except by way of justice and law: thus doth He command you, that ye may learn wisdom.
17:33-Nor take life - which Allah has made sacred - except for just cause. And if anyone is slain wrongfully, we have given his heir authority (to demand qisas or to forgive): but let him not exceed bounds in the matter of taking life; for he is helped (by the Law).
I am not a scholar, I have only been a Muslim for four years, but it seems that the Qur'an is very clear on prohibiting these kinds of acts.
Here is part one of a video from a sheik that I really respect, Dr. Tahir-ul-Qadri, at the release of his fatwa condemning terrorism.