Chino did pull the trigger and killed Tony, but he is not the only person responsible for Tony's death. Chino was simply seeking revenge for the death of his good friend and gang leader Bernardo. Bernardo had previously killed Riff which led Tony to kill Bernardo. So who is really guilty"

One possibility of who is guilty for Tony's death is Tony himself. He should not have gone to the rumble because for one he was not a Jet anymore, nor was he a Shark. He went there because Maria wanted him to stop the fight but he should not have gone anyway. Another reason why Tony could be responsible for his own death is he killed Bernardo after Bernardo killed Riff. He was not a Jet anymore so he should not be fighting on either side of the two gangs. One more reason Tony is guilty is...