Evil Within Secret Weapons (Spoilers and Question)

I am actually surprised not to find this discussion yet on the forums. So I have been playing "The Evil Within" and have recently beat the game. After I beat it I got 2 secret weapons to boot. But then I found out from a friend that there is other weapons
that he has unlocked after beating the game. This is what I have found:

Completion of game on any difficulty- Machine Gun and Rocket Launcher (Both are powerful weapons and extremely useful at many times, the machine gun can mow down huge hordes, but it is incredibly inaccurate. The rocket launcher is so powerful it can defeat
bosses in one or a few shots, the negatives are very slow reload time and can't move while aiming or use. Also neither of these weapons can't be upgraded, plus ammo is extremely rare.)

Collect all map pieces- 3 Round Burst Handgun and Heavy Sniper Rifle (The pistol is self explanatory and the sniper rifle is better balanced while it can go through multiple enemies, whats better too is that they run on their respected weapons ammo and follow
the upgrade system as well. (Pistol= Burst Pistol/ Sniper Rifle= Heavy Sniper Rifle))

From my friend that has finished it on "nightmare" difficulty:

Completion of "nightmare:" difficulty- Brass Knuckles (Greatly increases melee strength).

Now here is my question... There is one more weapon. Its called Joseph's Pistol (Automatic Handgun). Has anyone obtained this thing yet? Supposedly you"re suppose to collect everything that belongs in the archive and finish the game. But this is vague
cause I have finished the game twice (once normally and a second on new game+) and I have collected everything in the game. So what am I doing wrong?

:)

 

The Evil Within questions

 

Name an Achievement

Hear no evil, See no evil, Speak no evil (25G): Secret Achievement. Continue playing to unlock this secret achievement.

 

I haven't played it yet, but I just did a bunch of searching for you. I haven't seen anyone that has unlocked it. Is it even unlockable? Maybe it will be in future DLC.