What are examples of irony in "A Sound of Thunder"?

The most re-published short story in science fiction
history, Ray Bradbury's "A Sound of Thunder" deals with the idea of time travel and how
subtle changes in the past can drastically affect the future. A group of people book a
hunting expedition through a travel agency that takes them back in time--to kill a
Tyrannosaurus Rex. They are warned to stay on a designated path from which they must not
stray; any change made by a visitor from the past may cause untold changes upon their
return. (The T-Rex they plan to kill has already been determined to have died, so his
death--repeated over and over upon return trips--will cause no changes, the guides
assure.)

There are several examples of irony in the story.
Perhaps the most obvious is how the simple death of a butterfly millions of years in the
past can totally alter the future from which the travellers come. Because of the
butterfly's death, a different--and more dangerous--President has been elected; the
language has changed; and the town appears different. Also ironic is how the man who
accidentally kills the butterfly is punished in a like manner. A final irony is the
title, which refers to both the sound of the T-Rex and the gunshot heard in the
end.