Isn't it interesting how in recent decades the news has been filled with suicide bombers and others running into battle to kill or be killed in order to personally benefit themselves in their death?
The apostles, by contrast, did not want to die, they wanted to go on teaching -- to live. Yet, they did not fear death. They had seen Jesus render death as being of no affect. They were all eventually put to death for refusing to deny that they were witnesses of such a thing. Nor did they kill.
The reason they did not fear death is that they had seen a man who claimed he was sent by the Father, be put to death, and appear to them immediately afterward, just as he had told them he would. They had seen enough. God did not need them to kill, nor fear those who threatened to kill them, but only to believe what they had seen and been told in person. They could only keep telling others until their dieing day. They left the day of their martyrdom in his hands.