Hello, one of my family members ,had to be put on full life support,after not breathing for a long time (unknown amount),they say he may be brain dead,but he still has been getting goosebumps and sweating at times,they don't know why he has been doing this if he is brain dead, has anyone ever heard of anything like this?

Is there a possibility he has not lost all brain function,and could recover?
They say he has blood going to brain ,but its swollen and its going around the brain.