Facebook used to freeze an account when its owner died. It now allows users to designate a “Legacy Contact” to manage their Facebook account after they die. General Facebook policy shuts down a users account upon death, but many users would want their loved ones to be able to access their account to retrieve pictures or announce memorials. Of course, a shared password could accomplish this, too, but it obviously isn’t advisable to share passwords and the ability of a loved one to find or remember a password in the aftermath of death may be limited. So, Facebook has established a user preference setting to designate someone you trust to take care of this particular online asset.
More information and instructions can be found here: http://www.usatoday.com/story/tech/2015/02/12/facebook-policy-change-allows-one-final-post-after-death/23184757/