According to an in depth cable news report on the incedent, the 2 chimps simultaneously attacked from the front and back of the couple. The one in back first jumped the lady in a surprise attack, bit off her thumb and pushed her into her husband. The attack initially seemed aimed more towards her. Sensing this, the husband pushed her back to try to get her out of the way, which seemed to piss them off and they then concentrated on him.
It was reported he tried to "reason" with them during the early stages of the attack. It doesn't sound like he was in his most determined self-defense mode, not that it would have done him any good. Besides no weapon, he was extremely obese, so he probably couldn't move well. It was a slaughter. They easily took him down and quickly eliminated his ability to fight back...bit off all of his fingers, face, eye, tore off a foot as well as his genitals. Then were dragging him down a road.
The guy who shot them dead would probably have only gotten the first one if they were in the run from danger mode. Those things move faster than sh!t. You'd have to be damn good to get a sight picture, let alone a critical mass shot on a evasively moving/retreating chimp. These were not in the run mode.
A man moving against an attacking chimp would look like a sloth by comparison. They'd be past your stick or knife guard before you realized it happened. They're not just 4 times stronger, but 4 times faster. And are intelligent, cold blooded killers when they choose to be, just like humans. As in the wild, they flank their prey from different directions, and the one with the opening initiates the attack, takes you down, whereupon the flurry of threat elimination proceeds, usually unto death.