This is the nature of grief. Mourning often begins at the time of diagnosis and continues long after the person has died. It is often common for the surviving spouse, lover or friends to feel relief following the death of a loved one. This is likely to be true if dying has been drawn out and difficult. You may not believe death has really happened.
Some people experience disbelieve and shock.
It's not uncommon to want to deny that someone you've loved is gone. The lack of grief following a death may be a warning sign that you may have alot of difficulty later on. This may be a way to deny that someone we loved has died. While we all use denial and it is normal and often useful, we must remember that the pain is still there, even if we're not feeling it. You may notice others acting inappropriatly.