I wish I had a complete answer to your question, but to be honest, I don't -- not fully. Some day, in heaven, all our questions will be answered, including ones like this. But until then, we only know that evil is real, and we are not exempt from it.
What we do know is that death was not part of God's original plan for the human race. Instead, Adam and Eve were created to live forever, in perfect harmony with God and with nature. But something terrible happened: They rebelled against God, and sin -- like a deadly cancer -- entered our world. One of the most sobering phrases in the Bible is found in Romans 6:23: "For the wages of sin is death."
But we also know something else: God was not content to let the world stay under the curse of sin. Instead, He sent His Son, Jesus Christ, into the world to remove sin's curse of death and Hell -- and He did this by dying on the cross for us. And that's why one of the most joyous phrases in the Bible is found in the second part of the verse I quoted above: "But the gift of God is eternal life in Christ Jesus our Lord" (Romans 6:23).
God understands your heartache, and even your anger, but He still loves you, and my prayer is that you will turn to Him for the comfort and peace He alone can give. Even when we can't understand, He still loves us and will never abandon us.