An attack Sunday by Boko Haram Islamists who opened fire on students while they were sleeping in a college dormitory has killed at least 28 people, a hospital source told AFP. \"We have so far received 28 bodies. We have been asked to expect more,\" said the official at the Damaturu Specialist Hospital, referring to those killed at the College of Agriculture in Gujba, some 30 kilometres (18 miles) from Damaturu, capital of the northeastern Yobe state.