1 year old lab/pit mix incident?

 
1 year old lab/pit mix incident?
I adopted a Lab/Pit mix. He is now one year old and up until now has been a great dog. We go to the beach and the dog park and have never had a problem. He is very loving. I also have a boston terrier who is 3 and has been a great play mate to my lab/pit. Yesterday however for what appeared to be no reason at all my lab/pit mix charged at my boston and tried to bite him. Luckily i was there and was able to stop this, but now I am to afraid to leave them alone together. My boston has always been the alpha, with his litter who he grew up around, and with the lab/pit. My question is, how do i train my lab/pit that this is unacceptable. My two dogs have always played and wrestled together without any problems and normally the boston lets my lab/pit know when it gets to rough and he backs off. Is my lab/pit trying to gain dominance?? What do I do to stop this?
First of all, train YOURSELF to understand that PIT BULLS ARE BRED FOR DOG AGGRESSION. They should NEVER be left unattended with another animal. pets question and answers,www.5d2d.com

Are they BOTH Neutered? Your Pit/Lab is becoming of the age where tolerance of other animals becomes less. You have to manage this intolerance with training, supervision, and patience.


* Read through these pages for info on keeping the peace in multi-dog homes: (Specifically with Pit Bulls)

http://www.pbrc.net/multidogs.html

http://www.pbrc.net/rotate.html
you have to be the alpha, show both dogs that you are in control and they are to obey.