A short story about a scientist trying to prove faster than light travel. He uses a billiard ball for the demonstration. It works but the billiard ball passes through a rival scientist, killing said rival.
"The Billiard Ball" (1966) by Isaac Asimov.
It is written from a reporter's view. The reporter discusses the rivalry between the two men. The scientist is a slow theoretical thinker ("if you asked him if the Sun rose in the East, you could be certain that he had also considered the possibility that the Sun rose in the West"). The other is a fast practical thinker, an inventor.
The inventor asks the professor to try his invention, humiliating him - "even though he says it's impossible, he will now demonstrate it."
The catch at the end of the story is, the billiard ball goes straight through the rival's heart - and the video footage shows that the scientist had already aimed the ball there! Had he, for once in his life, thought really fast and realized that the ball would work as a bullet?