This is your Farmer on Drugs

“Whoa, mule! What's wrong with you?” McGregor said sternly. His mule had been more and more restless for half an hour now; probably spooked by all the dogs barking, he thought. Now a wind was blowing and the air had a nasty smell.
Reverend Smith was walking down the lane toward McGregor's farm, and started feeling light-headed. The air smelled funny, he thought. The trees seemed scared – this was strange. Scared trees? But the way they were moving sure looked like they were scared.
McGregor, seeing that no work was going to be done this morning thanks to that finicky, stubborn mule, unhitched it from the plow and started walking it towards the barn, leaving the plow in the field for tomorrow.
His head felt kind of weirdly strange a little as he unbridled the mule, and he started staggering. Everything looked funny; he rubbed his eyes and saw Smith staggering towards him. He giggled; Reverend Smith staggering?
“Are you OK, John?” McGregor said. “You look a little unsteady.”
Smith giggled. “You don't look so steady yourself.” They both started laughing uproariously.
“I don't know what's so funny,” McGregor said, and laughed again.
“Those cows are funny!” Smith said, giggling.
“Hey! My cattle!” McGregor exclaimed excitedly. “What's wrong with them?” The cattle were all spooked, terrified.
“Oh, Lord,” laughed the intoxicated preacher. “Look at that funny tree! It's sinking!” He started laughing again at the leaning, sinking tree. “That's hilarious!”
“Sinkhole!” McGregor yelled, and started running to the cattle pen's gate before falling down. He got up and continued to the gate, this time at a quick stagger. Smith sat down on the ground, his head spinning.
McGregor opened the gate, but he was too late for half his cattle, who had fallen into the ever-widening hole. It was certainly a sobering experience, even though he still fell down and laid there for a few minutes after opening the gate, not the least bit sober.
“Reverend!” he cried, when he started regaining his senses and saw the preacher laying prostrate on the ground. He felt like his head was clearing somewhat. A little.
Maybe.
Neither the farmers, nor anyone else yet, could have any idea that a supernova had obliterated the Acrux star system three hundred twenty one years earlier, and that the gamma rays from the supernova had just arrived at the solar system at the speed of light, killing everything on the southern half of all the system's planets and burning much of Sol's planets' nitrogen into many different and varied oxides.
Their ozone layers were gone, too, thanks to the chemistry caused by the combustion and the various chemicals that were released and mixed by it. It was the same on all the terraformed solar planets as well, and most likely other stellar systems also suffered the same fates.
Something similar, except it wasn't really, had happened more than once. An example was an exploding star that had affected the Earth four hundred fifty million years earlier, causing a mass extinction called the Ordovician event. This is only one of the many examples available.
What usually caused these mass extinctions on Earth was some angry, petulant, unsociable, mean-tempered, obnoxious, fatassed little superstar who couldn't hold his mass and finally blew up under the pressure.
This was not an angry, petulant, unsociable, mean-tempered, obnoxious, fat little superstar blowing up under pressure.
This supernova was man-made. And it was an accident.
Well, it was sort of an accident. Like World War One on Earth was started. Sort of an accident.
Or just maybe bad planning. But it doesn't matter, they had been dead for over three hundred years, and were not going to face the consequences of their actions, since they already had faced them over three hundred years earlier and were long dead.
Planets around stars that are near, cosmically speaking, these phenomena are greatly affected by them. On Earth-type planets, with mostly nitrogen atmospheres, much of the nitrogen combusted. The combustion produced various nitrogen oxides, mostly what protohumans who used hydrocarbons for fuel had called “smog,”
The oxide affecting McGregor's farm was what is commonly known to us as nitrous oxide. It had taken days to travel there from the southern hemisphere, and the oxides that reached them were at least improbable. But reach them they did.
“Laughing gas” is what nitrous oxide is usually known as.
“Reverend? Wake up! Are you OK? Oh, Yeshuah...”
The preacher's eyes fluttered open. “What happened?” he asked.
“A sinkhole in my cattle pen,” McGregor answered. “Whoa... look inside that hole!”
What appeared to be steam or smoke was wafting out.
“I think you might want to call a meeting, Reverend.”
“Yes, I think you're... Oh, Lord! Devils! Watch and pray, I'll get help. You might want to get your pitchfork.”
McGregor stared at the hole in horror as the reverend ran away.