(S (S (PP (IN On) (BASENP (NNP June) (NN 5))) (COMMA ,) (S (NP (BASENP (NNS gunmen)) (PRN (COMMA ,) (SBAR (WHNP (WP who)) (S (VP (VBD had) (VP (VBN posed) (PP (IN as) (BASENP (NN police) (NNS officers))))))) (COMMA ,))) (VP (VP (VBD raided) (NP (BASENP (DT a) (NN bus) (NN station)) (PP (IN in) (BASENP (JJ central) (NNP Baghdad))))) (CC and) (VP (VBD captured) (BASENP (NN 50) (NNS people)))))) (PERIOD .))