A mound isn't dead until its queen is killed. At the first sign of danger many ants will rush out to repel the invader while others carry the queen to safety. The queen also can fly. Root her out of one mound, and she'll fly off to start another. She can even mate while flying away to start another colony.
First ants can attack humans in swarms and with little warning.
The fire ant grasps the skin with its jaws and then injects its venom from the poison sac. It then pivots and inflicts up to seven or eight more stings. It feels like hot needles being plunged into the skin. By weight, fire ant venom is more powerful than cobra venom. Fortunately the ants are small.