2 1/2 yr old male boxer

Question
We recently got a 2 1/2 year old male boxer.  We were told that he had nipped a 14 year old boy.  After studying the police report and the officers study of the history of the dog we are convinced the 14 year old was instigating the bite by pulling on his ears and legs trying to get him to go out of the house.  We have him in our home now and he is great.  He is very protective of the children and even me and my wife.  He does growl when played with.  It is a very deep almost scary growl.  He has only done it twice as I do not like it and it sort of scares us.  Is this a normal behavior for Boxers?  We have only had him for 3 days and are nervous still about him but he is very impressive with his great manners.  We have a 1 year old and he will not bother her as of yet but she is not with him unless I am there.  The only other thing he has done is to fight with our lab.  I was walking him and the lab attacked and the leash fell of and they went at it.  I did get them apart and both only had minor scratches.  Is this correctable cause now he can't stand the sight of the lab.  I guess the big question is should we keep working with him or re-home him?  My 8 year old and 6 year old daughter have fell in love with him and I need some professional advise about what to do.

Answer
3 days is too early to make any decision.

Yes, Boxers growl when played with. Their moms teach them to be "big, bad, Boxers" and growl and play rough. You can modify that behavior by verbal commands in a stern, assertive alpha voice to stop using some keyword to signal him.

He is not aggressive but protective, and not as socialized as he should be with other dogs. This will resolve itself in your house with the lab as long as you supervise for awhile so they can get used to one another. Play with them together and get them involved in playtime and running in the back yard together- frisbee, ball, anything.

Keep working with him- use a whistle on bad behaviro: blow the whistle, command in a stern, assertive alpha voice, and leash him if necessary and remove him from the "crime scene" for 5 minutes then unleash him.

Soon, he will associate the whistle and being leashed to his bad behavior and stop.