This is a polar bear scavenging off of a bowhead whale
The thing that some people don’t understand about modern-day predators is that, very often, their prey gets eaten alive. Going to the ends of the earth to ensure your victim is dead has little tradeoffs and is a colossal waste of energy – if your prey is defenseless, why bother? For that reason, yes, bears (and most predators/omnivores) can and do eat their prey alive.
Death isn’t the end goal for most predatory attacks – for animals like, say, an African wild dog, immobilization is enough. As I mentioned, making sure a victim is dead is a huge waste of energy with very little payoff, so they might as well just start eating it.
As you can clearly see, this salmon is far from dead
And, as the image above clearly shows, there’s no point in ensuring that something like a salmon is dead. What’s it gonna do, slap you with its tail? Might as well spare the theatrics and just eat the thing.