Where did "Kaczynski vulnerability" come from? Your comment is the first result I got googling it.
"David Kaczynski had once admired and emulated his elder brother, but had later decided to leave the survivalist lifestyle behind.[74] He had received assurances from the FBI that he would remain anonymous and that his brother would not learn who had turned him in, but his identity was leaked to CBS News in early April 1996."