Are piranhas really man eaters or is that a myth?

They do not intentionally mean to eat humans but if they get a hold of the "scent" of blood one piraña will attack and make the blood spew out which draws the pack and if this happens the person I bit is dun fore. The only type that will attack is the razor-toothed piraña of the genera Serrasalums and the Pygocentrus nattereri who bite to kill