Google does a lot of things…
At this point nothing would surprise me 
Today we reached a notable future-history date in the writings of Ray Bradbury:
So I thought of this story, which I think was part of a collection of short stories sharing the same fictional universe. Mankind has space travel and also a medical device that allows you to live forever if you get regular injections. Some guy has a mental defect (paranoia?) which is subdued by the device, but because he ignores a broken warning light the paranoia resurfaces. He kills the wife of a friend, then flees in a stolen spaceship which sets course as fast and far away as possible. The (former) friend also follows him with another spaceship. The guy is cured in the spaceship by the device, and tries to contact the other guy by radio, but gets no answer. Many (thousands?) years later they are still following each other, the follower very slowly catching up with the former, and the guy realises that the other guy has died but the ship is following him automatically and will overtake him in the distant future, thereby killing him (as the ships project some kind of nuclear field that is their energy source and propulsion drive, and which would be lethal).
Larry Niven’s The Ethics of Madness
“The Triple Moons of Deneb II” by Daniel H. Charney from the Science Fiction Tales anthology edited by Roger Ellwood. I wouldn’t know this if I hadn’t read the same short story.
you can see illustrations from the story here:
Wow. That question has been unanswered for a long time. Thank you!
That’s it, thanks!
Short story, probably in Omni magazine. An engineer who’d worked on the Space Shuttle program was guilt-ridden after the Challenger explosion. He gets onto a plane and plants/brings aboard a bomb that will explode when the aircraft reaches an altitude such that it will impact the Earth, in the same amount of time it took Challenger to fall. I think the title was the number of seconds.
ETA: Never mind. I copied and pasted my post into the search bar, and AI returned Two Minutes and Forty-five Seconds as the title.