We adopted Oscar in 2015 as a sweet, shy, 7-month old puppy. He was called a "Lab Mix" by the shelter, but my extensive experience in with dogs tells me he most likely has some pit bull, boxer, maybe some type of hound and something with a curly tail in him. He seemed like the perfect dog for us (me, my husband, 3 kids, and our then-5 year old beagle mix, Marley). He fit right in, was wonderful with our kids and even the baby. When he hit adolescence however, he began displaying concerning behavior that I attribute to protectiveness maybe? He started acting very nervous around certain people and biting them. He bit a couple of kids and we put him in an I tensive training program for behavior modification. He did extremely well and made a lot of progress....but he still bites people. We can't figure out what it is that sets him off. It's men, women, black, brown, white, hats, no hats, adults and children (but never very young children, like under 5). And it's not everyone. He's always been fine with our extended family members he's known since we brought him home, and a handful of our friends. Some people just make him feel threatened and we don't know why. We have resorted to strictly keeping him away from other people, shutting him in our bedroom when people come over (and not having people over often), and not bringing him out in public. I know that's just reinforcing his issues, he needs to be socialized, but I don't know how to do that without risking him biting another person. We CANNOT afford another training program right now. The last one cost $2,000 and that is just not in the cards right now. I have alot of experience with dogs, having worked with them for 15 years, and I think I can handle training him myself, I just need some guidance. I have no idea where to start! Thoughts???