(S (S (BASENP (PRP They)) (VP (VP (VP (VBD came) (PP (IN under) (BASENP (NN mortar) (NN fire)))) (PP (IN at) (BASENP (DT the) (NN airport)))) (PP (IN during) (BASENP (DT a) (JJ hand-over) (NN ceremony))))) (PERIOD .))