 After a six @-@ year break , Kaczynski struck again in 1993 , mailing a bomb to David Gelernter , a computer science professor at Yale University . Though critically injured , Gelernter eventually recovered . Another bomb mailed in the same weekend was sent to the home of Charles Epstein from the University of California , San Francisco , who lost several fingers upon opening it . Kaczynski then called Gelernter 's brother , Joel Gelernter , a behavioral geneticist , and told him , " You are next . " Geneticist Phillip Sharp at the Massachusetts Institute of Technology also received a threatening letter two years later . Kaczynski wrote a letter to The New York Times claiming that his " group , " called FC ( an acronym that stood for " Freedom Club " ) was responsible for the attacks . 
