Who knows what happened... one minute lots of animals were calmly drinking at the watering hole and the next moment there was almost a stampede. First the impala flew in all directions then they spooked the giraffes that were just coming in for a drink. After the pandemonium where everything disappeared into the bush, they slowly reemerged and cautiously made their way back. No visible predators were around (like at other watering holes we visited). Maybe a small bird starting it all.