How would you describe the narrator's initial reactions after the killing?

Hey Greta, which chapter or story is this from in the book? 

it's a short story from my literature book.

Is it from the fist chapter? I need to know what killing it is? 

It's The Language of Litrature American Literature ...McDougal Littell...Unit Seven War Abroad and Conflict at Home...Comparing Literature...Traditions Across Time:  War in Vietnam  Part 1...Ambush (1990)  by Tim O'Brien  Short Story  page 1106-1108.

That's all the information I can provide.........Hopefully you can help me.....Thank You!