Coverage at 1b on walk

[outathm]

I have a mechanical question here. R1 on 2B. RB walks. BR rounds 1B and stops. Pitcher has the ball in the cirsle and is standing there with no motion or play attempt anywhere. I am BU and have taken my mask off and followed the BR to 1B. R1 takes off with the pitch and goes to 3B. Who's call is the hesitation (Circle violation, LBR) on the runner at 1B. I kind of feel like it's my call, but I so not want to poach on my FU's call. Thanks for the help.