need to unlock and restore ipad but don't have Apple id and password

I have an iPad that was returned by a former employee. I would like to restore it to factory and redeploy it to another employee. The Apple ID was the former persons email address which is no longer valid.

I get all the way to the 'Activate iPad' screen but it won't allow me to enter our company's Apple ID to restore. I'm totally stuck. This is NOT a stolen iPad. It is company property but this user locked the screen with a passcode so I cannot get into it at all.