People really misunderstand zoos and animals.
I'm sure the vandals had good intentions, but fuck them they're ignorant assholes.
Zookeepers have a strong bond with the animals they keep, I'm sure that the keepers are absolutely devastated by this news. Animals raised in captivity have very little chance of survival in the wild, this one lasted one year, after 13 in captivity. Sure, it might have been a pretty swell one year but also may not have been. It likely had to learn how to hunt from scratch, so it probably went weeks or months at a time starving because it didn't know how to catch live prey.
At the same time if it had stayed at the zoo, maybe it didn't have miles to fly around in but it was kept fed and clean, with regular veterinarian checks to ensure it's health was okay . Letting it loose was similar to leaving a dog out in the forest to die a slow and painful death.
Don't get me wrong, there are terrible zoos out there which don't deserve to be called zoos, but any of them that are AZA certified are generally pretty darn well managed and care for their animal's welfare both physically and mentally.