I have a little yellow lab mix who is a very sweet little pup. She is 2 1/2 and I got her from the pound about 5 months ago. The other day I got home from work and she bolted out the front door and the postman was in the front yard on the other side of my truck and I think that he startled her. She proceeded to latch onto his arm and break the skin on both sides of his forearm. She has shown aggressive behavior over the last week and a half and I'm hoping that this isn't her true colors starting to show through. I'm looking for any advise from people as to what I should do. Thanks for your help on this one!

I would call up my vet, make an appointment for a health check, and ask for a referal to a good dog trainer that uses positive methods.
Good luck.