Sorry, Silly Goose, but as a wildlife photographer, I know that the Oreamnos americanus - otherwise known as the mountain goat is not on the IUCN Redlist (Endangered) or Yellow List (At Risk). It may be disturbing to see a majestic animal like the mountain goat lying on it's side expired, but frankly with at 100,000 examples, there is enough genetic diversity to still be able to recover this animal.
Even the North American Black Bear that Booth baited and shot, was also not on the IUCN Red LIst. The population is stable and the reproduction rates are steady.
If you want to get really pissed off about something wait until he kills something that is on the IUCN Red List and then we can really crucify him with justification.
I'm confused as to why he's bragging about the rarity of the kill.