Let me also elaborate on my position:
1) In the end it may be for the best that attacks like these take place. It is a fact that our enemies may have been destroyed in the attack.
2) We should rejoice that our enemies are destroyed, but it should be for the glory of Hashem, and not because we did anything to deserve it.
3) We should consider the innocents who may have died in this attack, so that in the end it is for our best. Hashem has made all humanity and does not do so for the purpose of destroying it. That the innocent died with the wicked we should feel a little sadness about.
4) In cases of self defense we should be concerned with our own people first, others later. If 'Syria' attacks Israel then the entire population of syria should be dealt with with deadly force.
This is my general principle on this question.