The sound of the shell

In Chapter One, Jack is still an innocent. Sure, he puts on a show of bravado, but he is no more capable of killing a living thing than any of the other boys. Over time, and as things become more civilized, he can bring himself to kill...... in fact, he likes it. But in Chapter One, it just wasn't happening. 

"Because of the enormity of the knife descending and cutting into living flesh; because of the unbearable blood."