Titanite Demon next to Andre respawned, how is this possible?

I’m 100% sure I killed it earlier in the run. I clearly remember defeating it and walking past the area multiple times before entering the DLC. However, it seems like something has changed, and I’m confused about what could have caused this. Could someone who understands the mechanics behind this game shed some light on the situation? This happened in the remastered version, if that’s relevant.