The two chimpanzees pulled Oberle halfway under the fence by his foot and then used the space created by his body to escape the restricted area. They then dragged Oberle about 100 feet into the public area and continued to maul him.
"They have no anger," Cussons said of the chimps. "This is why we come to the conclusion, as far as our expertise goes, that it was a territorial defense. They directed the violence towards Andrew whom they feel was infringing on their territory."
The chimpanzee shot by Cussons after the attack was taken to the Johannesburg Zoo where he is healing, according to officials. Neither of the chimps will be euthanized.
Oberle has not been able to speak yet to explain why he went into the restricted zone. His friends in Texas are raising funds for his care and his father said he will likely return to his research work with the animals if he is able.
"I'm sure if he's able to do it, that he is probably going to be right back there when he can," Andrew Oberle Sr. said. "That is what he wants to be doing."
The institute also hopes to return to normal and return to its work of opening the world of chimpanzees to the public.
"We still maintain that we are a safe facility and that we need the support of the public also to understand that these are dangerous animals," Cussons said. "These are wild and dangerous animals and they need to respect the laws and regulations that we put in place."