it is possible that he developed liver failure in this short time.
Sorry for your loss. I will be praying for you. I am not sure what a TPN is ( I am not a doctor just on this site because my liver enzymes were elevated but I am believing the next test will be good as I had one of my Christian church Pastors prayed for me.) It seems very mysterious what you wrote and there must be a reason for the failure. I know different drugs can be harmful to the liver and poisons etc... Could your son have gotten a hold of something toxic???