(S (S (NP (BASENP (NN Security)) (PP (IN in) (NP (BASENP (NNP Copenhagen)) (PRN (COMMA ,) (NP (BASENP (DT the) (NN capital)) (PP (IN of) (BASENP (NNP Denmark)))) (COMMA ,))))) (VP (VBD was) (VP (VBN tightened) (PP (IN after) (NP (NP (NP (BASENP (DT the) (NNS attacks)) (PP (IN on) (BASENP (NNP London)))) (BASENP (NNP Thursday))) (SBAR (WHADVP (WRB when)) (S (BASENP (NN 49) (NNS people)) (VP (VBD were) (VP (VBN killed)))))))))) (PERIOD .))