when a bee hive / nest becomes over populated, several thousand will form a swarm and go in search of a new nesting site. The male "drones" will attempt to mate with the virgin "queen" bee and a few will be successful, dying in the process.

However, if all of them died, then that must have included the female "workers" (that would ordinarily from a new hive with the queen):

in the scenario you describe, I guess they came from a hive that had been sprayed with insecticide, and the swarm comprised fatally poisoned bees that were unsuccessfully attempting to escape to form a viable new colony.

The males, called drones, lead very short lives. Check some of the dead bees. I think you'll find that their compound eyes meet on the midline of the head, indicating that they are drones.

I was at work a few days ago and within like 30 minutes a massive bee swarm took place. They were All outside the walls and around the lights and stuff. Hundreds and hundreds if not a thousand or so bees just everywhere. Then some started crawling on the ground, which led to most if not all crawling on the ground. And then all of them died within an hour or so. They just swarmed, crawled, and died. They were in fetal positions squirming when they were dying. Nobody sprayed a thing on them. What the hell happened and why do bees do that?