Nightly News | July 01, 2012
>>> we're back now with an update on the brutal attack by chimpanzees on an american student in south africa . nbc went there today and learned more about what may have led to the attack.
>> reporter: inside the sprawling sank chctuary. today his doctors say he is stable.
>> after six hours in the operating room the doctors have attended to some fractures and attended to some of the wounds.
>> reporter: he was on a study trip, an anthropology student from the university of texas . just before the attack he was giving a lecture about their behavior to a group of tourists and then went across the fence. new eyewitness accounts suggest he may have done that to prevent an animal from hurling a rock at people.
>> it may have been instinctive for him to go for something which he thought was useful to do.
>> reporter: other staff members raced to rescue him they became targets, too.
>> kept pursuing me. i climbed back inside the vehicle. it jumped on the bottom of the vehicle and i closed my door and he started beating through the window.
>> reporter: chimps are highly territorial. there are 33 chimpanzees here. each one rescued from the entertainment industry . they are incredibly strong. some are seven times as strong as an adult human male. tonight his parents are on their way to his bed side as his long recovery begins.