curious ap report story senior u.s. official russia involvement syria gas attack official say evidence russia know chemical weapon attack happen associate press report interest couple reason release information senior u.s. official effort embarrass rex tillerson cause trouble trip russia tillerson russia 36 hours add tension could actually strategy trump administration give upper hand u.s. washington ap senior u.s. official say unite state conclude russia know advance syria chemical weapons attack last week.the official say russian-operated drone fly hospital syria victims attack rush get treatment.hours drone leave russian-made fighter jet bomb hospital american officials believe attempt cover usage chemical weapons.until monday u.s. officials say sure drone operate russia syria senior official say still clear fly jet bomb hospital.the official say presence drone coincidence russia must know chemical weapons attack come victims seek treatment.the official authorize speak publicly intelligence matter demand anonymity read ap senior u.s. official release damage information russian involvement syria gas attack