If you want to delete an existing user, you should be aware of certain issues. While deleting a user, there are chances that you accidentally delete all the posts made by that user.
To delete an existing user, just log into the admin panel and select the Profile menu. Select Authors and Users from the sub-menu. You will see all the available users in your blog. You can delete any one of them by checking the check box beside each of them and clicking the delete button at the bottom.
When you delete any user, the following screen appears asking you if you want to delete all the posts of that user.
You have two options while deleting a user. You can either attribute all his or her posts to another user or you can delete all the posts made by that user. Make a choice and click on the Confirm Deletion button.