To participate in Jihad.The media has been showing us all kinds of pictures, of them as friends, boxer, school life; Oh look, CNN has discovered wrestling pictures! You know, the investigators identified the bombers with the help of pictures that showed their pleased expressions after the bombs detonated. Wouldn't you rather see those pictures?
It is illuminating to note that the family is ethnic Chechen, the people who perpetrated the Beslan massacre. You should learn about that atrocity to know what is possible here.
Remember--there are no "innocent civilians" in Jihad.