Use other references value from firebase realtime trigger functions

Hi I started add some backend logic to my android app using firebase functions I want to use some value different then event data value

exports.makeUppercase = functions.database.ref('path')
     .onWrite(event => {
      const original = event.data.val();
      //I want to use value like this.
      const other_val= root.database.ref('path').val();
      console.log('email', "firms", original);
      const uppercase = original.toUpperCase();
      return event.data.ref.parent.child('uppercase').set(uppercase);
    });

I want to use other_valwith event data but so far I just using event data ref but I can ascend or descend in database event.data.ref using more parent or child. How can I solve it?

via ogulcan