The mood created in the story by the author is the horror of the civil war. Some of the words which contribute to that mood is "weird laugh," and "terrible laugh." They convey an atmosphere of strange and bad feelings. The verb "croaked out" also describes a rare feeling, given that human beings do not usually laugh as frogs. In addition, the adverb "suddenly" creates some suspense in the paragraph, which is not a positive feeling.
...croaked...
weird
terrible
...humor...
...sudden...
...tumble...
