First let me express my condolences on the loss of your son. There is very little I, or anyone else can say that will ease the pain. Only the love of Jesus, and time can do that.
Though I don't understand God's purpose or plans in calling him home so early, still I rejoice in the fulfillment of the Lord's plan, trusting that He will be glorified through this somehow."
Praise God that you understand this. God has a plan. We don't always understand it, we usually don't agree with it, but it's His plan.
In times like this, I believe, that person has done everything God had planned for him to do, and his work here is finished, and God has called him home to be with Him. He's in heaven. How can we be sad for that? Praise God that we have the promise that someday, we'll all see our loved ones again, "When the roll is called up younder."
"OH what a day, glorious day, that will be."