D.in our every deliberation, we must consider the impact of out decisions on the next seven generations
"A Sound of Thunder" is all about how the smallest event can have a huge effect. When Travis and Eckels time travel, Eckels steps off the path and accidentally kills a butterfly. This small event changes the events of the future and they see it when they return back to the present.
A. Travis shoots him.
The story ends with Eckels realizing the impact his actions have had. Travis comes behind him, clicks off the safety on the gun, and the last thing Eckels hears is the "sound of thunder". This is presumably the gun shot that kills him.
