(S (S (QT (DQL ``) (QTC (S (S (BASENP (PRP I)) (VP (VP (VBP do) (RB n't)) (VP (VB know) (SBAR (WHNP (WP who)) (S (VP (VBZ is) (PP (IN behind) (QT (LRB [) (BASENP (DT the) (NN attack)) (RRB ]))))))))) (CONJP (COMMA ,) (CC but)) (S (BASENP (PRP I)) (VP (VBP think) (SBAR (S (BASENP (PRP it)) (VP (VBZ 's) (NP (BASENP (NN one)) (PP (IN of) (NP (BASENP (DT the) (NNS factions)) (PP (IN of) (BASENP (DT the) (NNS ex-militants)))))))))))) (COMMA ,)) (DQR '')) (S (BASENP (PRP he)) (VP (VBD said)))) (PERIOD .))