(S (S (BASENP (NNS Officials)) (VP (VBD said) (SBAR (IN that) (S (BASENP (DT the) (NNS gunmen)) (VP (VBP appear) (S (VP (TO to) (VP (VB be) (VP (VP (VP (VBG using) (BASENP (PRP them))) (PP (IN as) (BASENP (JJ human) (NNS shields)))) (S (VP (TO to) (VP (VB escape))))))))))))) (PERIOD .))