Hi new member and first post. I have always had GSD and think they are such an outstanding breed. But I just had to put my 4 year old boy to sleep because of his aggression and I am torturing myself with how it could have been avoided. He was my most reactive dog ever. Anydog dog, person, squirrel, set him in a frenzy. We did obedience classes till he was about 3, then dropped them because he just couldn't advance and I knew at that point that I could never trust and show him competively. My dog club knew him well and always put him with submissive dogs so they wasn't a huge reaction at training. We did agility until a month before he died, he always had to jump the ring fence at least once and bark and assert himself at the other dogs. His behavior got worse. He was my running buddy and ran anywhere from 3-5 miles 4 to 5 times a week. I could never take him to the dog park. He bit a child when he was younger, and aggressively jumped on another while on leash and I was able to control the situation before he got bit. But the final straw was our daughters had their friends over, outside of our fence and as my girl was opening the fence to come into the yard he lunged out into the alley and attacked the two friends of theirs. Luckily I was right there, tackled him and only one got bit, no stitches needed, but I put him down immediately, never got to process it or think about it and now am wondering what more I could have done. He was bought from a backyard breeder and I will never make that mistake again. He was the best dog around his people but anyone else was seen as a threat. I want my next dog to be ok with my kids friends in the yard and am so scared of getting another aggressive dog (regardless of breed) again. Did I do the right thing? He was extremely bonded to me and I could have never rehomed him or given him to a rescue group. Thanks in advance, I know this was long winded. And for what its worth, in retrospect I think a different training club would have been a better choice for me.