It's hard to know what to say about events like the brutal murders in Itamar on Shabbat. Recently I picked up Rabbi Deutsch's book, Let My Nation Live, a narrative of the Purim story based on Midrashim and other sources. It talks about Amalek and their attack on Bnei Yisrael and how they (sorry to be so graphic) actually ate blood. Makes you wonder about the many blood libels and massacres the Jews have suffered over the centuries. As if to say, look who is accusing whom of killing children for blood! (We, who take pains to never ingest blood on principle).
My friend Channah sent me a Dvar Torah from Rabbi Eli Mansour about Purim as well. It said that Amalek attacked when Bnei Yisrael were expressing doubts about H-shem being with us. So our job in eradicating Amalek today involves removing doubt - having a Rav and asking him questions to remove doubt, and working on our Emunah (i.e. to realize on a higher level to Whom we are davening and improve the quality of our prayers). With regard to the recent tragedy I would add that instead of injecting doubt we should take the opposite approach and reinforce our commitment to route out evil, and redouble our hishtadlut to live in and build the Land of Israel.
I don't have the link on hand but I believe it was JEM in Crown Heights who put out a video of the Lubavitcher Rebbe ZY'A talking (in the 70s or 80s!) about the halacha that if a Jewish border city is threatened all we have to do is take up arms. H-shem will do the rest! I think we need to take this lesson to heart in terms of hishtadlut as well as in terms of Emuna.