Cellphone video captured a group of people knocking over a popular sandstone rock formation known as the "Duckbill" on an Oregon beach.
Oregon State Parks officials originally said they didn't think the break at the site frequented by tourists was caused by humans.
But the video shot by David Kalas of Portland shows a group of visitors pushing the structure until it crumbled to the ground on August 29 at Cape Kiwanda State Natural Area.
The sandstone pedestal was roughly 7 feet to 10 feet across and located in a fenced off section of the park.
Kalas told The Associated Press on Monday that he was with some friends making a drone video of their summer adventures on the Oregon coast when they went to the rock formation.
When they got the drone in the air, a group of eight people "came out of nowhere" and started pushing on the rock. Kalas says he started recording with his cellphone when it began wobbling.
"I didn't think anything would happen," Kalas said. "It's a big rock."
Five of the people stepped away, but when three others saw there was a crack, they pushed it over, Kalas said.
"We confronted them and they said it was a safety hazard," Kalas said. "They said one of their friends had broken a leg on it. It's like their weird revenge thing."
The Oregon State Parks and Recreation Department said Monday it will review the incident and takes vandalism seriously.
A similar episode in Utah caused an online uproar. Two Boy Scout leaders were sentenced to probation after recording themselves toppling an ancient rock formation at Goblin Valley State Park and posting it on YouTube.