He knows this about the killing of cities: Murder is louder than death. A burning home mocks a funeral pyre. The guilt of escaping under the cover of the ashes of everything you loved is heavy on your chest but you run just as fast. What you can take with you is not what you can hold with your arms.
He carries much with him as he flees the burning city.
But he doesn't know what he's carrying or where he's running to.
He does know not everything in his veins is human. He knows this because his fathers told him of this noble thing. He has a duty — a fate said his fathers — to save his blood and plant it far away where what it carries can grow and multiply. His fathers talked of his blood more than of him. In this and perhaps in most things they would have been hard to tell apart from the men who killed them and so many more in their indiscriminate wrath.
He has nightmares about this fate. He decides to mistrust his own counsel. When he chooses to travel to some place he turns around and goes in the opposite direction. Something happens, something always happens, and he has to turn back.
He falls in love in a city where he shouldn't have been. He doesn't think this love was put in him by his many fathers in the dead city. During a long night of storm and freedom he swears to stay with her for as long as they are both alive.
When dawn breaks he wakes up to see he has undone the parameters of his promise. His guilt is for a brief moment almost the match of his duty and he tries to attempt to take his own life. The inhuman thing in his blood overrides his mind and makes a decision, or some chemical balance shifts with the same outcome, that he is no longer to be trusted with his blood or his fate.
If somebody could ask his night self he would say he is dead. With horror and regret and shame at his relief.
He travels fast afterwards in a straight not unbloodied line to the strange city he was always going to, carrying in his blood death and the seed of the next dozen wars.