Also, online only. Unless there has been an update that changed this.
There's an offline bot mode now that they patched in. You can only play as Jason as far as I know. I think you can select the number of counselor bots and difficulty. I think they said that you can't play as a counselor because they couldn't get the Jason AI right or something. So, uh, yeah.
They're actually working on a single player "challenge" mode and previewed it in February, but they're still working on it. I guess it's supposed to be inspired by Hitman and involve you sort of stealth killing counselors as Jason, but it doesn't have a release date yet. Kind of ridiculous that they're basically still trying to patch in the promised rest of the game a year after its release.