They're referring to a niche academic term that has within the past few years started gaining usage outside of academia. It can be approximately defined as[0]:

> The use of mass public communication, usually against a particular individual or group, which incites or inspires acts of terrorism which are statistically probable but happen seemingly at random.

[0]: https://en.wiktionary.org/wiki/stochastic_terrorism

Only very loose connection to the stochastic processes of mathematics.