I can believe it. He was wandering around Iraq with electronic equipment and probably electronics repair equipment when he was picked up. When he revealed that he had been questioned by Iraqi police and the FBI had been snooping around, Al Queda decide that he had become a liability and decided to make his execution dual purpose.
During the third scene I doubt that he is drugged as he sits up on his own throughout the tedious propaganda speech and shifts around several time to try to relieve some physical discomfort he is experiencing. His head is erect and he appears alert. I don't think he was expecting what came next.
IMHO, the actual murder was botched as they zoomed in too much and were out of focus so they decided to do it again, this time with a beheading.
I wonder if Nick were under surveillance when he was released, and the intel is being put to very good use?