miriam: how did it change to the commitment to focus on in triggerpoints, behavioral threat assessment. was there more focused on it because of the increase in mass shootings and the high-profile nature of them? mark: leaders in the field of threat assessment i was speaking to around that time were expressing very stark concerns about the political dynamics in the united states and what that could lead to. they were essentially confirming that extreme ideology has -- as a factor in mass shootings was more on their radar. it was a higher level of concern. one thing i write about in the book is out no single thing is predictive of a mass shooting. it is actually a very complicated equation in terms of motive. why do people commit attacks like that? that is something i was interested in from the beginning and what drew me to the subject in trigger points. because at the field of work bringing together collaborative expertise to try to answer that question and act -- it can be very difficult in a lot of cases. there are cases where it is really almost impossible to say what the motive was.