The big Ohio story over the last few days involved an exotic animal owner who opened the cages of his private menagerie and then shot himself. The escaped animals included lions, tigers and bears (of course), wolves, baboons and monkeys. All were hunted down and shot. This has sparked some minor controversy about whether the animals should've been tranquilized instead, an argument which ignores both the facts of the escape and the practicalities of doing so.
First of all, police officers are not equipped with tranquilizer guns as part of normal procedure. The deputies that responded to a call of escaped wild animals carried assault rifles, as well they should have. There was no time to get the required equipment together, and waiting around to do so would've raised the possibility of an escaped animal injuring or killing someone in the meantime. This is plain and obvious.
Secondly, it took until Wednesday night to deploy experts with tranquilizer guns (the animals were turned loose on Tuesday). Should the police have simply let the animals run free in the meantime? Of course not. This is, again, obvious.
Thirdly, note the word 'experts' in the paragraph above. It's not simply a matter of handing guns to cops, once you get the guns, and telling them to tranquilize all the animals they find. The user of a tranquilizer gun basically needs to be part anesthesiologist, according to this site. You have to calculate the dosage based on approximate body weight, species and the concentration of the drugs you're using, which is an inexact process. And since (as a now-armed cop) you don't know exactly what animal you're likely to encounter, and thus what dart you'll need, there's a major risk to the cop AND to the animal. Shoot a dose intended for an elephant into a monkey, it probably dies anyway. Shoot the monkey's dose into the elephant, you just make it mad. And expecting somebody who's not trained with that piece of equipment to get it right, under pressure, for every animal is an unacceptable and unreasonable demand. I'm not saying I like the idea of exterminating the animals, but killing them on sight was by far the best way to ensure that nobody got hurt (and indeed, nobody got hurt with the exception of the owner, who apparently committed suicide).