Who should be notified?
Twitter, Inc. c/o Trust and Safety
795 Folsom St., Suite 600
San Francisco, CA 94107
Who can notify them? What documents are needed?
A family member can fax Twitter at 415-222-9958, email them at privacy@twitter.com or write to them at the above address. They will need the following information: the Twitter user name or a link to the profile page of the Twitter account, the family member’s full name, contact information (including email address) and his or her relationship to the deceased user. In addition, a link to a public obituary or news article about the deceased should be provided. Once the information has been received, Twitter will remove the account or assist family members in saving a backup of the user’s public Tweets.
If no password, can survivor receive one? How?
Per Twitter’s privacy policy, they cannot disclose account information or passwords to anyone, even after an account holder dies.  The next of kin won’t have any access to the account owner’s direct messages and can’t send a message informing the followers of a death.
Process for inactive accounts?

Inactive accounts will be deleted after six months.