Why?

Joshua McGinley stared at his wife. He knew she'd just said something important but for the life of him he couldn't work out what she meant.
"Jesus!" Cole breathed out noisily as he said it. He understood immediately, her words merely confirmed what the last fifteen minutes had hinted at.
Zeke bowed his head.
"You didn't have to kill Anna, Ma," he muttered, almost to himself, his words barely audible. "She would have kept quiet. She did keep quiet." He dropped to his knees and covered his wet face with his hands, "Why'd you have to kill her, Ma? Why?"