Theodore John Kaczynski aka the "Unabomber" is a former mathematics professor, a domestic terrorist, and serial killer who between 1978 and 1995 killed 3 and wounded 23 others by attempting to start a nationwide combing campaign targeting people involved with modern technology. 
Kaczynski was found dead in his prison cell on June 10, 2023.

Handwritten note from Kaczynski informing the prison mailroom to slip this inside of an envelope.