Mac Mini admin password issues

I was given a mac mini by my job as they were going to destroy it. The issue I'm having is the Mac is set to a user who no longer works for the company and no one knows the admin password. I cant add users to the account as he locked that function and I am unable to do reset the password. What can I do to get this computer back to factory reset so that I can put my credentials in? Any advice or help is appreciated.