Some factors to consider -
Gross or microscopic instability, or bullet "yaw", plays a very large part in internal destruction. When a bullet is just microscopically off its gyroscopic axis, it almost always destabilizes and kicks sideways upon striking a body; from a few degrees to ninety degrees or more, and presenting more bullet surface to the tissues and thrashing them as it moves through the body.
Next, large grievous wounds are due to the liquids in the tissues and cavities. The liquids are put in motion by hydraulic effects, and the destructive effects of tissue and organs will extend in all directions far beyond the initial wound axis. The stomach and intestinal tract, particularly when occupied with a recent meal, is especially dangerous since they could not only be explosively destroyed, but also serve as sources of further bodily destruction with 'secondary missles' of food particles and/or liquid.
The .224 diameter projectile, however it is loaded, is certainly capable of all of the above.
Gross or microscopic instability, or bullet "yaw", plays a very large part in internal destruction... That's the same unsubstantiated hype put out by everyone from McNamara's underlings in the 1960's to the gun writers of today. My experience is that a .224" diameter bullet at about 3,000 feet per second just doesn't cut it or real, living beings. Regardless of how it works in ballistic gelatin, all of the wound channels I've cut out of the deer that I've shot with a .223 show markedly less disruption than those from equivalent .30" diameter bullets. Whether the bullet is going straight, sideways, or fragmented, the wound channel is simply much smaller than those that get 90% kill ratios. Assuming this shooter isn't getting head shots, I think he is using a faster round than a .223 Remington.