(S (S (S (BASENP (DT The) (JJ second) (NN bombing)) (VP (VBD took) (BASENP (NN place)))) (SBAR (WHADVP (WRB when)) (S (BASENP (DT a) (NN suicide) (NN bomber)) (VP (VP (VBD detonated) (PP (IN in) (NP (BASENP (NN front)) (PP (IN of) (NP (BASENP (DT a) (NN police) (NN headquarters)) (PP (IN in) (BASENP (NNP Dera) (NNP Ismail) (NNP Kha)))))))) (S (VP (VBG killing) (NP (BASENP (NN 17) (NN police) (NNS recruits)) (SBAR (WHNP (WP who)) (S (VP (VBD were) (VP (VBG taking) (NP (BASENP (DT a) (NN test)) (SBAR (S (VP (TO to) (VP (VB join) (BASENP (DT the) (JJ local) (NN police) (NN force)))))))))))))))))) (PERIOD .))