Can / how do we know what death is? This question may read a little philosophical, Buddhist, and personal.

I've been a little obsessed with death for a very long time, and feel like I have zen answer. Less interested in "the path" (I would like to practice zazen) than whether my conclusion is sound, though to an extent, if it is, I can go on my way. As well as whether it conflicts with any zazen practice. A Buddhist friend keeps telling me I'm afraid and trying to outsmart death, and they say nobody really knows, which I definitely sympathise with, but equally I believe I'm right. 

So how can we know what will happen to us at death? Do we ask a teacher, ourselves, not ask about it, not worry about it, or something else entirely?
'Death' happens to a 'person', 'self-entity' or 'self'.

When the mind is free from thoughts of 'self', it will know 'death' only happens to a 'self'. 

It will also know when the mind is free from 'self', there is no 'death'. 

The 'termination of life' is not the same as 'death'. 

These things the mind can know when entering into 'emptiness' (śūnyatā - 空).