(S (S (BASENP (NNP Afghan) (NNS rioters)) (VP (ADVP (RB also)) (VP (VBD claimed) (SBAR (S (BASENP (JJ U.S.) (NNS troops)) (VP (VBD had) (VP (VP (VP (VBN shot) (CC and) (VBN killed)) (BASENP (NNS civilians))) (PP (IN at) (NP (BASENP (DT the) (NN scene)) (PP (IN of) (BASENP (DT the) (NN accident)))))))))))) (PERIOD .))