As non-STEM majors know all too well, math can be a dangerous subject.

Nobody knew about those dangers more than former Penn State professor Patrick C. Fischer, who was a target of serial domestic terrorist Ted Kaczynski, also known as the “Unabomber.”

According to the New York Times, the Unabomber mailed and hand-delivered 16 different bombs between 1978 and 1995, often targeting high-profile professors and scientists. As a self-proclaimed primitivist, the bomber’s reign of terror was an attempt to slow the development of modern technology and industrial development.

As a leader in the theoretical computer science field, Fischer became a quick target for an attack. A few years after graduating with a Ph.D. in mathematics from MIT, Fischer found his way to a position as Penn State’s department head of computer science.

Fischer left his position at Penn State to become a department chair in Vanderbilt in 1980, but the Unabomber was none the wiser.

In 1982, a suspicious package mailed under a false name arrived in Happy Valley addressed to Prof. Fischer of Penn State’s computer science department. Since Fischer had since relocated to Vanderbilt, a postal worker forwarded the package to Fischer’s new address.

When the package eventually arrived in Nashville, a secretary, Janet Smith, opened it since Fischer was lecturing in Puerto Rico. Opening the package triggered a device and the small box exploded, sending Smith to the hospital for three weeks, according to the Los Angeles Times.

Fischer, while physically unharmed, spent years trying to figure out why he was the Unabomber’s fifth target. Although they may have been in a similar place at the same time, Fischer and Kaczynski never knew each other. Fischer eventually came to the conclusion that it was because his professional career “went from pure math to theoretical computer science.”

The former Penn State professor went on to do important work in database theory that eventually assisted in developing modern search engines. Fischer died in 2011 due to stomach cancer, according to his family and the New York Times.