A Long Way Gone is Ishmael Beah's firsthand account of life as a child soldier in the army during Sierra Leone's brutal civil war against militant rebels in the 1990s. He was trained to use an AK-47 at a very young age, and while he initially was fearful of it, a vicious combination of drugs, American war movies, and the desensitization that resulted from routine killing eventually turned him into an awesome killing machine with it.

The book does not mention a specific "last time" that Beah fired his AK-47. It's not as though he had some epiphany after killing a rebel and laid down his gun for the last time. The last specific mention in the book occurs near the end of chapter 14. Beah suffered from insomnia, largely as a result of the horrific images imprinted on his fragile psyche. Late at night, wide awake, he would hear noises in the wind that sounded like the humming of a boy named Lansana he used to know who was gunned down by a rebel. However, he mentions that he would simply fire his gun into the air and the humming would go away.

Chapter 15 then begins with a brief recap of the next two years,taking us to 1996 when Beah was 15. He talks in general terms about being a killing machine and feeling pity for no one. He opines,

The villages that we captured and turned into our bases as we went along and the forests that we slept in became my home. My squad was my family, my gun was my provider and protector, and my rule was to kill or be killed. The extent of my thoughts didn’t go much beyond that. We had been fighting for over two years, and killing had become a daily activity.

From this statement, we can assume he fired his AK-47 many more times in the act of killing.

However, it is shortly thereafter, also in chapter 15, that Beah and his fellow child soldiers arrive in a town called Bauya for supplies at the same time a UNICEF truck shows up. An army lieutenant decides they have served long enough and tells them to lay down their guns and leave with the UNICEF people. Just like that, Beah's killing days were over.