This is rural (or at least semi-rural) Louisiana.
For all we know, the property could have been neglected or sitting vacant for an extended period of time. Maybe a new owner just bought it, and got the fright of his or her life upon opening the door to the shed. Or maybe the shed was simply never used, and was far enough from the house that the owners never noticed any unusual number of critters.
When i was much younger, i worked for a couple of summers as a waiter and bartender in a nice country house hotel in the English Lakes District. It was a job where a lot of the staff lived on-site, and for a while i had a room in the hotel itself, rather than in the separate staff quarters. It wasn’t like a guest room; more like the rooms of the staff at Downton Abbey, on the top floor of the building, at the back.
One morning, i found a couple of European wasps in the room. I assumed they had gotten in through an open window, so i got rid of them and forgot about it. The next morning, there was another. And the morning after that, i woke just in time to see one of the little bastards sink its stinger into my bare chest.
After yelling in pain, crushing the attacker in my bare hand, and throwing it with all my strength against the wall, i set about making a closer inspection of the room. I noticed that the opening in the ceiling, leading to the attic, had its cover very slightly askew, leading to a small gap. I assumed that this is where the wasps had got in, so i adjusted it to close the gap.
But i also went to the head groundskeeper/maintenance guy to tell him that there might be a nest up there somewhere. He called in a pest control person, and they found a huge nest up in the roof. Until i raised the alarm, no-one had noticed it, because the wasps had been able to come and go under the eaves, without getting into the main part of the building. It was only the mis-aligned cover in my room that allowed them in, and gave the game away.
The exterminator took care of them in short order.