Aggressive dog only when owner is home

Thanks for your comments! I think you're both right in that the dog is perceiving my presence as a threat or potential indicator of something bad (maybe his owner leaving town etc) and that there probably isn't much I can do myself. My friend hasn't really put any effort into training the dog and pretty much spoils him and lets him run the house so I'm sure that's a big part of it as well. I've suggested he get some professional help training but he doesn't seem to take it seriously enough. I was thinking maybe if I had some treats with me or something every time I walked into the house the dog would start to associate my presence with something more positive. Interesting he has two dogs (brother and sister) and the female dog absolutely loves me and always jumps up and rolls on her back and even pees a little out of excitement when I come in. Two totally different reactions and temperaments. I know that the aggressive male dog was hit by a car before my friend adopted him so might have some residual trauma from that.

/r/Dogtraining Thread