Alma experienced a symbolic death, described in the intense imagery of eternal torment and the pains of hell (v. 13), phrases typically reserved for post-mortal damnation. The emphasis is not intended to be on the pain but rather on the awakening of his soul to the need to repent. The pain comes not because it is externally applied, but because “I did remember all my sins and iniquities.”
In verse 14, Alma states that he “had murdered many of [God’s] children, or rather led them away unto destruction.… ” He does not explain his meaning here, but the fact that he rephrases “murder” as “leading them… into destruction” negates the idea that Alma had literally killed anyone. He does, however, consider his action as being criminal if he kept them out of heaven. Understanding that he may have played a role in their possible eternal damnation inflicted such pain on him that he wished to become “extinct both soul and body.”