In all seriousness, I believe liability would fall on me since the customer issued the warning in the beginning. If he wasn't warning people of possible dangers on his property, then it'd be different I'd imagine.
Actually, it's probably the contrary. The customer has acknowledged that he has a "dangerous animal" on his property and failed to take reasonable measures to protect people from it, i.e. keeping it caged. This is similar to cases where people put up "beware of dog signs" and their dog bites someone. The sign can be used as evidence that they were aware they had a dangerous dog.