That sounds proper unsettling, the dogs reacting is what gets me. Animals don't lie, they pick up on things we can't and if both of them were fixated on the ceiling that's not nothing.
Had something similar a few years back, my old terrier would not move from one spot in the hallway for about three nights running. Just staring at the wall. Never did figure out what that was about.
Did you manage to get any photos or audio? Even a basic recording on your mobile can sometimes pick up frequencies you wouldn't catch with the naked ear. I've been experimenting with long exposure shots aimed at areas where my dogs show interest and a couple of times I've caught what look like faint anomalies in the frame, probably nothing but worth doing.
What did the walking sound like - heavy, or more like something light moving quickly? That detail might help narrow down what you're dealing with.