What constitutes sufficient proof to mandate the killing of the animal involved in bestiality?

Primary text

The killing of the animal is not required until the act is established through clear evidence (bayyinah). If the perpetrator confesses, and the animal belongs to him, the act is established by his confession. If the animal belongs to someone else, the killing cannot be enacted based solely on his confession, as this constitutes a confession against the property rights of another, which is not accepted, similar to confessing ownership of property belonging to a third party.