Package JSON script for Firebase Emulator

I am trying to add a script to run the emulator with the downloaded key from Google Platform but I'm having some trouble targeting the json file. It is placed in the same directory as the package.json file

This is on a Windows machine

"scripts": {
    "lint": "eslint .",
    "serve": "firebase emulators:start --only functions",
    "shell": "firebase functions:shell",
    "start": "npm run shell",
    "deploy": "firebase deploy --only functions",
    "logs": "firebase functions:log",
    "emulator": "set GOOGLE_APPLICATION_CREDENTIALS=key.json && firebase emulators:start"
  },

npm run emulator

!  Error: Failed to read credentials from file key.json : Error: ENOENT: no such file or directory, open 'key.json '