Hang on. Something has occurred to me. When he listens for Ricks heartbeat has it occurred to anyone that he might have been checking to see if he was dead to alleviate his guilt for what he was about to do anyway? Not entirely sinister as he knows he can't drag Rick, gurney and all, out of a hospital with zombies, trigger happy national guard and general chaos all around. He puts that table in front of the door to give him a fighting chance but his mind seems made up concerning Ricks fate.