Originally Posted by
Labradorks
It sounds like play, over-excitement, just inappropriate play. Adding a choke chain or prong collar and correcting this will make it worse, especially if it is aggression.
My advice would be to videotape it happening so you can show that to your vet, or better yet a behaviorist or someone well-versed in Labs so they can tell you if this is play or aggression and help you move forward.
What is his lineage? How is his breeder? Have you contacted her? What were the parents like? Since you got the pup at six weeks, I am having doubts about his breeding, meaning that temperament of the parents were not taken into consideration. I could be wrong, but a pup going to his family at six weeks just sends up a lot of red flags.