He did so because one of the brothers did not have photo identification nor could he understand English, and because the agent found both of the passengers to be suspicious.
( He ( ( did ( so ( because ( ( one ( of ( the brothers ) ) ) ( ( did not ) ( ( have ( photo identification ) ) ( ( ( ( nor ( ( could he ) ( understand English ) ) ) , ) and ) ( because ( ( the agent ) ( ( found ( both ( of ( the passengers ) ) ) ) ( to ( be suspicious ) ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (PRP He)) (VP (VBD did) (SBAR (RB so) (IN because) (S (NP (NP (CD one)) (PP (IN of) (NP (DT the) (NNS brothers)))) (VP (VBD did) (RB not) (VP (VB have) (NP (JJ photo) (NN identification)) (SBAR (SBAR (SINV (CC nor) (MD could) (NP (PRP he)) (VP (VB understand) (NP (NNP English))))) (, ,) (CC and) (SBAR (IN because) (S (NP (DT the) (NN agent)) (VP (VBD found) (NP (NP (DT both)) (PP (IN of) (NP (DT the) (NNS passengers)))) (S (VP (TO to) (VP (VB be) (ADJP (JJ suspicious)))))))))))))) (. .)))
The agent thought the passengers were suspicious because of the way they were acting.
( ( The agent ) ( ( thought ( ( the passengers ) ( ( were suspicious ) ( because ( ( of ( the way ) ) ( they ( were acting ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT The) (NN agent)) (VP (VBD thought) (SBAR (S (NP (DT the) (NNS passengers)) (VP (VBD were) (ADJP (JJ suspicious)) (SBAR (IN because) (S (PP (IN of) (NP (DT the) (NN way))) (NP (PRP they)) (VP (VBD were) (VP (VBG acting))))))))) (. .)))