Who actually killed Jesus?
Many blame the Jewish people for putting Jesus to death. That is unfair and inaccurate. The Jews did not do it. The Romans were more to blame, but even they weren't really responsible for it and did not bring it about. They were not even capable of doing so. As for who it was who put Jesus to death, it was primarily God the Father, not the Romans or the Jewish authorities. It was He who punished Jesus in our place to pay for our sins. God the Father deliberately offered Him up for our sake, just as Abraham was told to offer up his son, Isaac.
That said, Jesus' death came, in the end, when He gave up His own spirit. He did so because His mission was complete. He had finished the job that His Father had asked Him to do. He had paid the full penalty for the sin of the world.
28Later, knowing that all was now completed, and so that the Scripture would be fulfilled, Jesus said, "I am thirsty."29A jar of wine vinegar was there, so they soaked a sponge in it, put the sponge on a stalk of the hyssop plant, and lifted it to Jesus' lips. 30When he had received the drink, Jesus said, "It is finished." With that, he bowed his head and gave up his spirit.
John 19:28-30 (NIV)