pretty much when it comes to the larger scary animals. the grizzly, the wolf, mountain lions, polar bears, etc. are all routinely put down in these situations with little or no public resistance because they have been so effectively vilified in popular culture, tradition and even religion, that the gut reaction tends to be fear and not empathy. while that may not be true for us, we are still in the minority, and even the growing admiration for such animals tends to be thrill or fear-based, like "look at that big thing kill that other big thing, kewll!" rather than any sort of sympatico or care. all that combined with that 'taste for human blood' bullshit mythology that almost everyone still believes, and in this case acts on.
as for the national park service or fish and wildlife, i learned long ago when trying to help some wolves in idaho that had strayed off their allotted territory and ultimately received the same outcome, that these agencies are not as staffed by hippy vegan animal rights advocates as many people might think. they are just as often, if not more often peopled by hunters who view themselves as 'conservationists', or even just 9-5'ers that lack any visible ideology on the subject at all. even the laws on the books are only so good until someone looks the other way, and looking the other way for something like this, or knocking down eagle roosts by developers to avoid protected status laws like i used to see fairly often, is as commonplace as the euthanizing of grandparents with morphine in hospitals to clear bedspace. people who live in the few areas of wilderness-plenty often don't give a shit about scarcity everywhere else, hence the hunting & logging practices in sarah palin's alaska, the amazon, and the south pacific.
admittedly, habitat destruction has a far greater effect than particular cases like this, but it is precisely the mentality that allows cases like this that leads to that. if people don't value a single life enough, they won't value the many lives in an entire ecosystem when someone wants to develop it or cut a highway through it, dump in it, etc.
there may be a web of life, but there's also a web of death, and it's based on greed, stupidity, sadism, apathy, and indifference, the vanguard of this sixth great extinction.