ABUJA, Nigeria (AP) — Gunmen attacked a high school in northwestern Nigeria before dawn on Monday, taking 25 schoolgirls and killing at least one staffer, authorities said of the latest abduction of students in the region . No group immediately claimed responsibility for abducting the girls from the boarding school in Kebbi state and their motivation was unclear. Nigeria is facing a multidimensional security challenge , specifically from amorphous groups of armed bandits who specialize in