(S (S (S (BASENP (QP (RB About) (NN 350)) (NNS militants)) (VP (VBD participated) (PP (IN in) (BASENP (DT the) (NN attack))))) (CONJP (COMMA ,) (CC and)) (S (S (BASENP (NN 15) (NNS guards)) (VP (VBD were) (VP (VBN killed)))) (COMMA ,) (SBAR (IN while) (S (BASENP (QP (RB about) (NN 1,000)) (NNS prisoners)) (VP (VBD escaped)))))) (PERIOD .))