A cat who had become aggressive at home and bitten its owner's elderly father. They wanted it euthanized but because it was a bite situation and was not up to date on its rabies vaccine we had to hold it in quarantine for a time. Sadly, the cat seemed perfectly nice the entire time she was boarded with us. I had avoided interacting with her as much as possible, knowing it would break my heart if I got to know her. When I pulled her out to be euthanized she was purring the entire time, right up until she passed. I don't know how people who work in shelters cope emotionally.