Monsters disappear after death

[theybegone]

So I'm not sure if this is a glitch or just how the game is supposed to be, but whenever I get killed by a monster the game will reload at some checkpoint a little while back, but once I get back to the place where the monster should be, it just isn't there any more. If the monster had destroyed a door or something, the door would also still be gone.

Is this a glitch, or just the way the game is? I would like to actually play through the game and not just get a free pass every time I mess up. What I end up having to do is just quit to the main menu and reload an older save, which is usually way back at the beginning of the level/section, and I really shouldn't have to do that.

So is this a glitch? Or did I accidentally put on super easy mode or something?