Why was the Old Man repeatedly saying that he was only taking care of the animals in Ernest Hemingway's "Old Man at the Bridge"?

Surrounded by war, the old man faces likely death from an enemy whom he doesn't even know. In effect, he is pondering why he deserves death in this war. He has committed no crimes and was only "taking care of animals" prior to the arrival of enemy forces. At seventy-six years old, these animals were his sole responsibility remaining in life. His days were spent caring for them, not engaging in any conflict that should necessitate his death.
His comments also show his personality. He deeply cares for the animals and worries about what will become of them in his absence. He knows that the enemy line, and therefore the bombings, are coming ever closer, and the animals are in danger. In an effort to save his own life, he has likely sacrificed the lives of his animals, and his comments reflect that this decision weighs heavily on his mind.
It is unclear what becomes of the old man or his animals, but his comments point to the devastating effects of war on the most innocent of creatures.