Jesus had told the crowds that he would be crucified (John 12:30-34) but that no one would take his life by force. He said he would lay it down and take it up again (John 10:17-18). We usually associate this with his refusal to deliver himself from the Roman's hand and to go willingly to the cross. And we are correct.
But there is another aspect of his laying down his life and no one taking it from him. John tells us, "Jesus knowing that all things were now accomplished, that the scripture might be fulfilled said, I thirst.". The soldiers gave him a taste of sour wine, and after Jesus tasted it he said, "It is finished". And bowing his head he gave up his spirit".
He chose the moment for his spirit to leave his body. Jesus had to die before the two thieves so that his legs would not be broken. Every moment of the crucifixion was planned by the Trinity and every moment of the plan was fulfilled (Acts 4:27-28).
