[HELP] My Corgi Puppy Attacked and Killed My Pom

Hi! My corgi puppy is almost 9 months old and a few days ago, he attacked and bit my male 9 year-old Pomeranian. We hadn't noticed that the Pom entered the room and the corgi attacked the Pom as the Pom was passing by. He was not provoked by the Pom in any way. It took us a while before we were able to separate them. The Pom sustained injuries on the back and sides of his neck. Unfortunately, the pom didn't survive the attack (he died a day after) :(I've had my corgi puppy for almost 3 months now and I've given him basic obedience training and consulted with a trainer who, upon spending four hours with him, said he was a good and obedient dog (though sometimes he liked to challenge me). My corgi is generally friendly with other dogs especially when we take him outside. We have had no experience with him displaying aggressive behavior towards other dogs. We also have two pugs (male and female) and he gets along with them okay and has never tried attacking them.There has been a history of my corgi going after my Pom and only that Pom. I noticed that after a month of having my corgi, he would go on top of the pom and would try to hurt the pom. These happened around 3 more times and each time, I heavily scolded my corgi. The Pom was never injured since we were always quick to separate them. Since then, we let them out separately or in separate areas of the house. Generally, the Pom is very submissive when the corgi is trying to hurt him. However, when the Pom is in his crate, he would sometimes bark and growl at my corgi when we were simply passing by and my corgi wasn't even minding him.Now, my mom and the rest of my family is threatening to return my corgi puppy or give him to a new owner, both of which I'm heavily against and is not even a possibility that I'm considering. They fear that he will attack humans next, even if he's never shown human aggression. My family thinks that since he's had experience in attacking and killing another dog, he could easily do it again and hurt people next time. I don't think this is the best solution and it's really painful to lose both dogs.How can I proceed from here? Do their fears have a huge possibility of occurring even if we are vigilant and give him more training (which I'm really going to do)? Any insight will be greatly appreciated.Since the incident, I've made sure to keep my corgi leashed when he's not in my room and I always keep him with me. Also, I've talked to the breeder of my corgi and he said it could possibly be due to my corgi being territorial and seeing my Pom as a threat since they were also both boys. via /r/dogs http://ift.tt/2r0O02Y