(S (S (ADVP (RB So) (RB far)) (S (BASENP (NNS authorities)) (VP (VBP have) (S (ADVP (RB yet)) (VP (TO to) (VP (VB identify) (NP (BASENP (DT the) (NN three) (NNS people)) (SBAR (WHNP (WP who)) (S (VP (VBD were) (VP (VBN killed)))))))))))) (PERIOD .))