KABUL - Mohammed Naser heard the bomb go off and ran to his second-floor classroom window, just in time to see the cinder-block garden wall blow apart. The lights went out and students rushed for the stairway, but someone said gunmen had entered the first floor.
‘‘We were trapped. Girls were screaming in the next classroom. I could feel the fear,’’ Naser, 21, a business student at the American University of Afghanistan, said Thursday morning, hours after militants bombed and stormed the campus Wednesday evening.