It is funny when we thought that someone is dead and we are all wrong. If we make an inspection, we know that the person is dead when his heart stops beating. It is quite true if we call the person is dead. Somehow, there are things that make them is not dead at all.
Technically, we store every memories with the person we love. Nerves that we have can easily triggers the memories. Sight will bring back the love memories. Smell will bring back the sad and romantic memories. And if someone had blood bonds biologically is a half copy of the dead person. In some extreme ways, the bone cells can be used, though to make a DNA copy and recreate the dead person.
Technically, we are emanating energy to everything around us. Those energies are some stored in people around us, specially those who are close to us. Remember that energy cannot be destroyed, then it made us live in others immortally. Knows that we are bouncing every photons that ever touch our skin. Those photons have the exact copy of our appearance, and again, as long as we are not die around a dark matter, we can quite sure that the photon is not destroyed.
No one has ever really died. No one, based on the theory above. And somehow we all live forever.
When does a man die? When he is hit by a bullet? No! When he suffers a disease? No! When he ate a soup made out of a poisonous mushroom? No! A man dies when he is forgotten!