Four people were arrested Saturday on suspicion of vandalizing the Skyfari Aerial Tram at San Diego Zoo, triggering a shutdown and causing some passengers to be stuck on the ride for up to two hours, KTLA sister station KSWB reported.

The four men arrested were all aged between 20 and 24 years old, according to San Diego police. A San Diego Zoo spokeswoman told FOX 5 the four were “rocking back and forth” in their gondola, which caused the system to shut down automatically shortly after 2 p.m. Their identities were not made publicly available.

Fire crews were called in to rescue more than 100 passengers from the gondola ride, San Diego Fire-Rescue Department said in a tweet. The ride, which features 28 total gondolas that hold up to four people each, typically takes about eight minutes to make a round trip at the zoo.

One of the passengers stuck on the ride was annual zoo ticket holder Hussein Alhamadami and his girlfriend.

“We were just hoping that we were going to get down soon,” Alhamadami said. “It would swing back and forth for a few seconds and then it would stop.”

He said that at the time, it wasn’t clear to passengers why the Skyfari gondola had stopped.

“They were staying stuff on the speaker,” he said. “I couldn’t really hear so I had to call customer service and they said it would take about 20 minutes but unfortunately, it took about two hours.”

Firefighters remained on the scene until all guests were safely on the ground as of 4:34 p.m., the agency said. No injuries were reported.

But as time went along Saturday, Alhamadami said feelings of fear were starting to creep in.

“It’s happened to me before at a different theme park — not here — but this was worse just because we were up in the sky almost,” he said. “We saw people waving their hands at us. It wasn’t that bad at the beginning but we started getting worried towards the end.”