Dear Grieved, I won't say that I know how you feel because I have never lost a child. But I lost a sister who I was very very close to and I lost my husband 6 months later and I wanted to just crawl into a hole and die right along with them. I knew of God at the time but I didn't "know Him", but I do now. In my grief came anger, hopelessness and the fear of being along, but in the mist of all this I began to call on God and the more I called on Him, He came to me. Call on Him and He will meet you at the level of your sorrow and began to minister to your broken spirit. In Isaiah 61:3 To appoint unto them that mourn in Zion, to give unto them beauty for ashes, the oil of joy for mourning, the garment of praise for the spirit of heaviness; that they might be called trees of righteousness, the planting of the LORD, that he might be glorified. In Matthew 5:4 Blessed are they that mourn: for they shall be comforted.
Father, I come to you now in the Name of Jesus, to interceed for this person who is greiving for her lost child, I ask that You begin to minister to her spirit now and let her know that she is not along. I ask in the Name of Jesus that You let her recognize and feel Your loving arms around her. I ask that You give her a garment of praise in place of her heaviness. In the Mighty Name of Jesus. Amen.

Friend, know that He will never leave you, nor forsake you. He is your Father, so do as your son would do as a little child when he was hurt or afraid. I am sure that he would come and crawl up onto your lap and let you comfort him. So you do the same, "Crawl up onto Daddy's lap and tell Him all about it" and He will comfort you. Find joy in the fact that though your son is dead, he gave life to those people that received his organs. Be Blessed. 

Father, you said our tears you will wipe away. I am asking that you touch this dear one, and sooth him with your holy spirit. Father, remove the pain and fill it with the Joy that only comes from you in the name of Jesus!
Let him be a witness for you,
so that you may be lifted up and receive all glory! In Jesus Name Amen!! Weeping may edure for a night but joy will come in the morning!! 

Father, I pray for this dear one. I lift her to you and ask that you be her comfort and peace today. Thank you for her unselfish act and that so many were helped through her loss, help her now to rejoice in you and look forward to the day that her son and her will be reunited in heaven. I praise you Lord and bless you. In Jesus Name. Amen.