Right. Though I ran into a bug in the Newgrounds version:
When I killed the first soldier, no key was dropped and I was locked out.
I swear, I checked if the key wasn't somewhere else.
Viewing post in Return To Wolfenwald - Snow Island v1.0. comments
That is definitely a bug, the key should appear every time because player can't move forward without it. It could be a WebGl thing if you are talking about the web version, there are some issues with guns disappearing after the switch, player moving forward after cut scenes and collision problems that doesn't appear in desktop version.
Gonna look into that soon, gun reappears when fired and after-cut movement stops when opposite direction is clicked but key disappearing is a showstopper. Luckily these happen only in WebGL version, unless player is a Mac user there is always a Win desktop build. Also I'm gonna try and compile an Android version, probably there will be a whole new set of different bugs in that one :)