Death unfortunately is a common occurrence around here. Animals with severe injuries will die on their own, or sometimes mistakes are made that may cause an animal's death. Many times an animal will come to the center with an injury that is so severe that rehabilitation is just not an option. Other times an animal will be rehabilitated but won't recover enough to be released back to the wild. In those cases an alternative home--such as a zoo, or other place that houses animals for education--will be found. With the more common animals, like some owls and raptors, it is difficult to find an institution that needs an animal such as that. When this scenario happens the animal is put down.
So far I have witnessed several animals be euthanized, and it can be difficult to watch. I have had to assist with a couple, holding the animal while the injection was given. We euthanized a raccoon a couple days ago who had broken its back. I wasn't quite prepared for the process of euthanasia of this particular animal. After the drug had worked through its system, it continued to take residual breaths after it had offically died. The movements were very exaggerated and choppy as it opened it's mouth again and again in an attempt to suck in air.
This type of field truly isn't for the faint of heart. You have to be prepared to watch things die, sometimes in your very arms. On the other hand, there are many cases where you are successful in returning the animal back to its natural habitat, and that is the best feeling in the world.