Not necessarily, since :
- A culprit in this game is defined as "One who has murdered one of the game's victims."
They didn't kill one of the game's victims, so they're not culprits.
They're not victims either, because :
- A "victim" in this game is defined as a human in the story who has been murdered by one of the game's culprits.
- There are exactly three victims in this game!
Since they're not either victim nor culprit, they also bypass the rule that :
- No victim died as a result of suicide. I will extend this to accidents, heart attacks, or any other way of dying without the will of a separate killer.
Thus, they can commit suicide.
Now, I don't know if there's a red truth that everyone in the room was dead, so they don't necessarily need to kill themselves. Further on, they can also enter themselves in the bathroom and lock themselves in there (through the use of the quote that "- Each bathroom door can only be locked or unlocked from inside the bathroom.")