I'm not a fan of how (some) police use various forms of force, but I think shooting was justified in this instance.
To those who think the cop should have incapacitated the naked, bloody, face-eating man in some other way: It is fairly common for people in a psychosis to exhibit strength far above what they would normally be able to call on. They are also very unpredictable, and there is absolutely no guarantee they will take the sensible option. So it would be extremely dangerous to get up close, and even a taser might not work -- adrenaline and complete obliviousness to the situation can keep a person going despite repeated shocks.
The officer was also in a situation where had to do
something immediately, or risk the death of someone who wasn't engaged in brutally assaulting anyone. Bullets were the only reliable way to take the assailant down, and even took several of those to do the job. He gave the guy an opportunity to stop with the face-eating, but when that wasn't taken up he wasn't left with much choice

.
To those who think the cop should have aimed limbs rather than more lethal areas: Aside from the practical difficulties in doing so, there is a legal side to it. For good reason, a gun is always considered a lethal weapon (unless it's being used as a club

). That means that using one is only justified when killing the target is justified, and trying to merely subdue them would mean that level of force wasn't necessary, thus making it illegal. I hope you've all followed me here

. Same goes for knives, BTW.