Watch a Tsunami-Like Shelf Cloud Close In on Sydney, Australia

Beachgoers in Sydney on Friday were surprised by an ominous sight in the sky: a shelf cloud moving quickly over the water and toward shore.

The strange meteorological phenomenon, often topped with a thunderstorm cloud, sent people running off Bondi Beach as it rapidly approached land, some of them running up to a cliff to watch the scene unfold, CNN reports. The massive clouds eventually unleashed a heavy storm on the city—but not before eyewitnesses got some stunning photos and videos of the impressive event.

Officials announced a severe thunderstorm warning and urged people to stay inside, away from the windows, with their electronics unplugged.

[CNN]