cairo militant gunmen kill 300 people attack mosque egypt north sinai friday carry islamic state flag 25 30 number public prosecutor office say statement saturday gunmen wear mask military-style uniform surround mosque block windows doorway open fire inside automatic rifle statement cite investigation interview wound survivors number 25 30 carry daesh flag take position front mosque door 12 windows automatic rifle statement say use arabic term islamic state militant gunmen egypt mosque attack carry 'islamic state flag prosecutor