Game Situation: Double Play?


With R1 on first base and no outs, the batter (B1) hits a weak dribbling ball down the first base line. Both B1 and R1 think the ball will easily go foul, so B1 stays in the batter's box and R1 stays standing on first base. The pitcher fields the ball in fair territory just before it goes foul and throws to the first baseman. The first baseman catches the throw with his foot in contact with first base and then spins and tags R1 (who is still standing on first base). 

What should the field umpire call?

Is the outcome different if the throw from the pitcher pulls the first baseman off the first base bag, so the first baseman first tags R1 and then tags the first base bag with his foot?

Call
When the pitcher threw to first base, that retired B1. That also removed the force on R1, so R1 is protected if he stays in contact with any base -- so in the first scenario, B1 is out but R1 is safe.
 
In the second scenario, R1 is forced to leave first base on B1's fair ball, so R1 is no longer protected while standing on first. R1 is out when he is tagged and then B1 is out when the first base bag is tagged. We have the umpire's favorite play -- two outs on one pitch!