It is currently possible but you have to hit practically every shot perfectly. I'm currently working on an update which'll make this encounter easier as it's something I've heard a couple of times now :)
Man, sorry, it was 3 am and I completely rage quit the game after replaying it like 8 times over. It really is good up to that point. I always think it's weird when people tell creatives how to "fix" their work, but since your updating it anyway, a small animation or even a blood splatter on the screen could go a long way with making sure the player knows they are doing something. Also, I'd either put like a checkpoint there or an invisible wall between the "entity" and the player because my first go around I was standing right up against the door and insta-died. Thanks for the kind response, keep up the good work.
It's been a very tricky balancing act, I want it to feel like a skin of your teeth moment where you only just succeed. There is feedback with blood splatters and damage animations, but it's hard to see and hear when the gun recoil kicks your camera away and the shotgun blast muffles every other sound.
I'm not planning on adding checkpoints to that section, and an invisible wall I feel would detract from the tension if you hit one, and thus you know something's really up. So the plan for this next update is to make the fight more fair and have some more room for error.