A lion attacked and killed an American woman on Monday as a tour guide drove her around a South African animal enclosure, police and park officials said.

"The lioness approached from the passenger side and bit the lady through the window," said Scott Simpson, the assistant operations manager at Lion Park, which is an open-air facility north of Johannesburg.

The tour guide was in serious condition at a hospital, and sustained arm injuries from fighting the lion off, according to The Independent.

The park's website guarantees "super close-up views" and promises that guests can "get closer to a pride of lions and other animals and still be completely safe."

The woman, who was in the passenger seat of a car and has not been identified, died while emergency services were treating her. She was 22 years old.

"Our staff working at the top of the camp tried to get the lion away from the car. Ambulances were called immediately but it was too late," Simpson said.

Visitors to the park are told not to leave their windows open, as unprovoked attacks can occur.

"We make it so clear," Simpson added. "We put signage up everywhere that people must keep their windows closed. We hand them a slip of paper when they enter the park, I really don't understand why people think it's okay to leave windows open."

This is the third attack at the park in the past four months.

The lion responsible for the attack will not be euthanized, but could be moved to a private location, Simpson told ABC News.