Have you heard about the piranhas before?

Their aggressiveness is legendary. They have large triangular teeth sharp as razors planted on a jaw powered by very powerful muscles.

 This allows them to snatch flesh pieces very effectively.
Unlike most carnivorous fish, piranhas hunt in schools. their aggression is linked to the breeding period or the males keep the eggs.

They live in the rivers and streams of South America and are attracted by traces of blood and disturbances in the water.
A reliable source speaks of an agouti, a rodent of 45 kg, reduced to a skeleton in less than a minute.