This is topic that i personally have faced since the passing of my father early 2005 from throat cancer. I personally thought I was dying from the same cancer until I finally made myself believe that I am not dying. Thank God at the time, I had an awesome friend of Christ who helped me make sense of it.
At the same time that Death is final but it is also final resting place where people who were in pain can finally stop being in pain. I know my father was in a lot of pain before he passed away so knowing that pain is over is a nice relief also.
I know a lot of people ask the question “Why does God take people the way they do when they know they have a long life ahead of them?” which I honestly do not know the answer but i know that if God did take them then he did for his purpose and his glory which all of us have a hard time wrapping around our fragile minds.
We also need to remember that God did promise that one day we will be risen again and be with the Father forever in heaven and one thing we can be certain that God does keep his promises as we look to his soon life/death and resurrection as an example.
Please God look over us especially a good friend who lost his Father today for strength and understanding that he is know in a better place. Lord, also look over the family to give them strength in this trying time. Amen.