Bearded dragon overexposed to the sun! HELP!?

My bf's baby bearded dragons (1 mo and 4mos) were left exposed to sunlight for about 20 minutes.. after that when he came back, one of them died and the other is still breathing but it seemed that he had a really really bad sunburn! He barely moves and his skin is a stiff! We immersed his half body in a shallow basin of water..

Help! Can he still make it?? What can we do??