When 26-year-old Andrew Oberle, of San Antonio, began volunteering at the Jane Goodall Institute in South Africa, he knew the risks of working with chimpanzees.

But even animal experts say what came after -- a vicious attack on the University of Texas-San Antonio student -- was uncommon.

Grabbed under a secure fence and dragged nearly a half-mile and then mauled, Oberle has now undergone six hours of surgery and remains in a medically-induced coma.

His parents have flown to the Johannesburg hospital where he is expected to recover, albeit with permanent injuries.

Oberle also volunteered at the San Antonio Zoo for years and was beloved by the staff there for his devotion to animals.

Zoo Director Steve McCusker says, “I was surprised. It shouldn’t have happened. And maybe there were some extenuating circumstances that I’ll never know anything about, but it’s a shame that it happened.”

McCusker also notes that chimpanzees are not part of the zoo in San Antonio, in large part to the financial burden houses them presents.

He says because of their strength and volatility, they are difficult keepers.

“They are incredibly strong. They are (as much as) nine times stronger than we are. They just need to have room. They need to have separation space,” he said.

Those are all things that existed at the Jane Goodall Institute, making Oberle’s attack further distressing to friends and family.

They have set up a Facebook page to help pay for his medical bills.