Base on Balls Trick Play

[Coach1249]

What is the correct ruling on the following play. A pitcher issues a base on balls. The catcher throws down to first, the first basemans keeps the ball in his glove. The batter trots down to first, steps on the bag and steps off for a moment. The first baseman tags the runner. Is the runner automatically out? Does the runner need to have the intention of going to second to be called out?

Thanks for any help