HARARE, Zimbabwe (AP) — A bull elephant charged a truck that an 80-year-old American was riding in with other tourists on a game drive in a Zambian national park, flipping over the vehicle and killing her, a safari company said.

The attack injured five others on March 30 in the vast Kafue National Park, which covers 22,400 square kilometers (8,600 square miles) and is one of Africa’s largest animal reserves.

According to the safari company Wilderness, the “aggressive” bull elephant unexpectedly charged at the truck, which was carrying six guests and a guide on a morning excursion through wild areas.

It wasn’t clear what upset the bull. But in a video widely circulated online, the pachyderm is seen menacingly charging through the bushy terrain toward the tourists’ vehicle. A man is heard shouting “hey hey hey,” in apparent but futile efforts to scare it away. It reaches the truck and flips it over using its trunk.

Another female tourist was seriously injured and flown by helicopter to South Africa for treatment while the rest were treated for minor injuries, the company said.

“This is a devastating incident for everyone involved and we are doing our best to support the family and all affected,” Tarryn Gibson, the safari company’s head of communications told The Associated Press on Thursday. Gibson did not identify the tourist who was killed, and said her family wished for privacy. The company also asked people to not share the video of the attack online.

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While many wildlife parks in southern Africa teem with dangerous animals like elephants and lions, such incidents are rare, although they sometimes do occur with fatal consequences due to the unpredictability of wild animals.

Keith Vincent, chief executive officer of the safari company, said rough terrain minimized chances of an escape.

“Our guides are all extremely well trained and experienced, but sadly in this instance the terrain and vegetation was such that the guide’s route became blocked and he could not move the vehicle out of harm’s way quickly enough” he said.