Not sure what brought this thought about.

It's a sure thing that we are instinctually afraid of death. However, when (ish), or at what developmental stage, do we first intellectually grasp our own assured personal death?

Example, there were several close deaths when I was very young. I hazily remember grasping the concept of death as the end of life, that is a "bad thing" that can happen. I do not recall a time though when I learned that it's a "bad thing" that is GOING to happen to everyone, nor the time when I learned that it's GOING to happen to me. Nor do I remember any time freaking out about grasping my own mortality.

So now I'm curious. What age (about) and what else is going on developmentally at that time?