You saw it....
"That's one of our spears!" He screamed it, like a woman. "One of our own—from the front!"
"I let them get as close as I dared," said the Officer tonelessly. "I tried to find a way. But there wasn't any way but the ladder, and that was what the Piruts wanted. That's why they made them come."
Kirk's voice wasn't a voice at all. "You killed them. You killed my father."
"Three lives, against all those back on the plain. We held our fire too long as it was, hoping. The Piruts nearly broke through. Try to understand! I had to do it."
Kirk's spear made a flat clatter on the stone. He started forward. Men moved in and held him, without rancor, looking at their own feet.
"Please try to understand," whispered the Officer. "I had to do it."
The Officer, the bloody wall, the stars and the cold grey gullies all went away. There was nothing but darkness, and wind, a long way off. Kirk thought of Pa coming up under the wall, close to safety, close enough to touch it, and no way through. Pa and Frank and Russ, standing under the wall, looking up, and no way through.
Looking up, calling to the men they knew, asking for help and getting a spear through the heart.
After that, even the wind was gone, and the darkness had turned red.