(S (S (S (SBAR (WHADVP (WRB When)) (S (BASENP (NN customs) (NNS officers)) (VP (VBD surrounded) (BASENP (DT the) (NN vehicle))))) (COMMA ,) (S (BASENP (DT the) (NN driver)) (VP (VBD went) (PP (IN into) (BASENP (NN reverse)))))) (COMMA ,) (SBAR (WHNP (WDT which)) (S (VP (VBD led) (PP (TO to) (S (BASENP (NN two) (NNS officers)) (VP (VP (VBG opening) (BASENP (NN fire))) (PP (IN on) (BASENP (DT the) (NN vehicle)))))))))) (PERIOD .))