I never figured out if the guy got a dog that was ill-tempered, or if he made it ill-tempered. But my apartment building (loved the building, hated the neighbors) had no weight limit on dogs (learned after moving in, I had no pets so never even checked the policy). My first encounter with this particular dog was walking from my car in the parking lot back to the building. I heard it growling, guy held it on the lead while I made a brisk walk (not run) to the building.

My second encounter was actually inside. I lived on the first floor, not sure where he lived, but he was coming the opposite direction with the dog. It started dragging him, I hustled up the stairs (I was next to them, fortunately) while he regained control and got it outside.

The third encounter was the one I mentioned. I had returned from the gym (I walked there, it was a mile away) and was at the entrance when I heard the dog to my left. I looked and it was pulling on him, then it was free from him. Fortunately it had about 100' to cover before it would get to me and I got inside in a hurry (keypad entry, so at least there was no fumbling with keys and locks).

I really never wanted to be within 100' of that dog again, but they wouldn't evict him even after that incident. I moved a couple months later.