The sheriff is one crazy fella. He hid the bomb under his hat.

I knew he was the one coming up with this explosive plan when he smiled after PJ told them to move to the other corner.

Both Bertram and Smith were kinda worried but the sheriff, nope, he just keeps on rocking his hillbilly attitude and shrugs it off like a boss. 

PS: I want to note that just after Patrick calls the sheriff to set the meeting, Bret Stiles receives a note "Patrick Jane is looking for you". If we assume that RJ and Bret are related somehow (blood? friendship? idk), maybe RJ isn't *that* evil after all....he cares for his beloved mentor (father perhaps?).