Hello guys, I think i finally found how happens the weapon glitch (many people have reported over the years that you can get BOOH weapons when playing regular painkiller, but could never explain how).

Here is the way i found to replicate :

1. start a new run (sign the pact)
2. finish cemetary
3. at the beginning of atrium do a quicksave then a quickload (important!)
4. once the quickload is done, press escape and click 'return to the map' then reload atrium
5. you now start atrium with all weapons (including booh weapons)

PS: It seems to work with pruned savegame on my computer which is great, i would like you guys to confirm that it is not just my computer being funny.