-14120 (edspermissionerror) on delete user account

I am trying to delete user account which has been created for the postgres.

1. When trying to do it from Users&Groups i am asked for password (not clear message "You need their password. Please enter your password to allow it") - neither my admin password nor login password of the postgres account are accepted.
2. when trying to do through terminal getting error "-14120 (eDSpermission error) " after providing admin password
3. when trying to use Directory utilities - by clicking on "-" nothing happens

I did all required action to uninstall / remove all data related to postgres.

Any advice i can remove this user account?

Thanks in advance!