Are you actually asking this? Like why should people be worried that a disgruntled highly motivated person would venture into this area? Because it can happen. The outcomes of it could be really bad? It also doesn't have to be done by an individual, could be nation state or organization led. There are groups of people who believe humanity needs to end and all sorts of crazy stuff. Some of them have gone on mass murder suicide missions.

2 bad things can be threats at the same time. Even 10,000 things can be.