Justin Bieber -- Dad Allegedly Hurled Dog Off 2nd Story Balcony

Justin Bieber's dad flew into an angry rage and threw the dog he and Justin adopted off a second story balcony ... so claims the dog trainer who now has the pooch.

Justin and Jeremy Bieber bought Karma, an American Bulldog, a year ago, and it was rough from the beginning. Karma was living at Jeremy's Canada home, but the animal needed training. It bit Justin's little bro Jaxon, which sent Jeremy into nuclear mode.

Trainer Trevor Dvernichuk tells TMZ ... Jeremy grabbed the dog and hurled him off the balcony into a snow bank. Trevor says Jeremy then told him to take the dog and not to bring it back until it was socialized.

Fast forward to this weekend. Trevor still has Karma ... it appears it was pretty much abandoned by Jeremy and Justin. But Jeremy pitched a fit after Trevor started telling people that the dog was flat out abandoned. Jeremy now says Trevor stole the dog and he's getting the cops involved.

Trevor originally told us ... he's concerned about the dog's welfare because of what Jeremy did, but he doesn't want to get in trouble with the law so now that he knows Jeremy wants the dog back he's willing to return it. However, on TMZ Live stated lawyers will be getting involved and he may want some money for his services and the care of the animal.