It's definitely possible. I just always thought of the knife as extra-special like the Colt. We don't have the long history like we do for the Colt, but the fact that no one else seems to have ever heard of killing a demon makes it seem to me like it's a special case, like demons don't normally ever die.
Re: John's and Mary's absence from heaven (small spoilers)
It's definitely possible. I just always thought of the knife as extra-special like the Colt. We don't have the long history like we do for the Colt, but the fact that no one else seems to have ever heard of killing a demon makes it seem to me like it's a special case, like demons don't normally ever die.