Black bugs in house and outside/help
Here in NM, we had a 'wet winter' and a tremendous population of assorted mustard plants in bloom in spring. As those flowered, fruited and went to seed, they died, so insects associated with wild mustards were left hungry and homeless.
Our pests that emerge from the root zones of these dying plants are known as 'false chinch bugs.' I'll be yours are the same thing---but maybe a bit darker in color.
Our 'herds' of bugs can consist of hundreds to thousands of bugs that behave the same as yours are doing. They mill around and make you think you're having a sunstroke or similar.
I suspect you have the same thing.
Insecticides may kill a few of these bugs but populations are so large that the dead are quickly replaced by reinforcements. Spraying anything is fruitless and expensive. Our advice here is---leave them alone, plug the spaces under and around doors with towels or cloth (whatever works and stays put) and be patient. They will go away in hours or sometimes a day or two.
Occasionally I see plant damage that might have been caused by these bugs, but the bugs won't be present to confirm that association. They do not always do damage---so patience is the key here.