This is the logic behind the "climate of fear" the media creates—every time a tragedy is made into a huge news story, it becomes semi-permanently available as an exemplar to your brain of that kind of thing happening; and then, when you try to figure out when the last time that kind of thing happened was (which is, in turn, a heuristic people tend to use for how often something happens) the highly-available exemplar in your mind makes you still feel like it "just happened" even if it was years ago.
(Or, to put that another way: everyone in America who was alive when 9/11 happened, still thinks of terrorist attacks against the US as happening far more often than they do; everyone in America who was born after 9/11 has a better-calibrated estimate. The scope of the tragedy—and especially of the reporting of the tragedy—caused it to be "too available" to people, permanently biasing their time-scale and frequency estimates.)