Poll....Positioning

[Bandit]

Curious....Runner on second, no outs. BU in slot behind shortstop. Batter hits grounder to SS. SS checks runner back to second and throws to 1st to get BR. Runner at 2nd goes for third, 1st baseperson throws to third to try for tag out. BU calls BR out....Poll Question ?? Does BU turn and make call at 3rd or does PU come up line to make call...Have asked this question last couple days at games with different umpires and get different answer...Book I believe says PU...Have found this to be good pre-game discussion.