[KevinP73]

The guy that was "attacked" was new to the crew. He has experience with big cats but not these specifically. The lion was doing what big cats do and that was establishing his position in the pecking order. The new guy was just there for the animals to get used to him. When the big cat first turned to him and made contact the new guy raised his chin, sometimes seen as an act of aggression in the animal world. Had the lion really wanted to "attack" the guy he wouldn't have gone for his leg, he would have gone for the throat (ala Siegfried and Roy). The lion was just showing the guy that he was the biggest MALE in the room.
The guy did the right thing though by leaving the room once he lost control of the situation it could have gotten real ugly had he stuck around trying to appear dominant.