Christians, how can I help my child who is having nightmares about Jesus sending people to hell?

My child is 8 years old and goes to church with one of his friends every sunday only to wind up becoming terrified of this lord Jesus you folks worship. My wife passed away some time ago and she was a very kind person but not religious in the least bit. My son approached me about 2 weeks ago and told me that his mommy is burning in hell for not accepting Jesus and I was shocked by what he said. I told him that we are all children of God though he is convinced that she is burning in hell and has been experiencing nightmares so severely that I have had to take him to a shrink. I no longer allow him to go to church for it has only made matters much much worse. I am considering putting him on medication due to the fact that his anxiety concerning hellfire and brimstone has been ripping him apart from the seams. How could anyone believe in something so heinous and then decide to poison my child's mind with this ideological sickness after my son is still dealing with his mother's death?