How does one deactivate a dead person's account on FACEBOOK?

I am this person's mother. I have tried for years off and on to get someone at FB to deactivate his bogus account, which he didn't even create, to no avail. He died long ago. He died before the account was even created! This is very painful for the family. How do I go about resolving the issue? The last time I tried (when I belonged to FB), they told me I had to have the email and password for the account, which of course I don't know. HELP!