Welcome to YT!!!!
I agree with some of the other posters, it sounds like Killer has too much freedom this early in the game. Crate training would probably be a good idea for you, if you're able, but staying in the crate for eight straight hours would be a strain on his little bladder. Have you considered litter box training him? This was the issue that I ran into with Silvia, who is very small (less than 3lbs) and I was always worried about her having to hold it for so long. DH and I both work full-time and Silvia is alone from 7AM-3PM everyday. The litter box option has been a wonderful solution for us, and we actually made it a permanent one, because it worked out so well. Here is my post on it, in case you're interested:
Litter Box Training Your Yorkie