When pet piranha attack

Some idiot abandoned two pet piranha in a Hong Kong fountain and one took a bite out of a boy's finger while he was playing in the water.
The piranha -- which has its origins in warm South American rivers and can devour whole cows when hunting in packs -- is a popular fish in Hong Kong home aquariums and can be bought in Mongkok pet shops for less than HK$100 a pair (7 pounds).
Maybe piranha could help deal with the problem of the renegade alligators in New York City's sewers. Link