Held Ball on the throw in????

[splitveer]

A1 is the thrower for a spot throw in. B1 is guarding the throw on the inbounds play. A1 reaches ball through the boundary and B1 grabs the ball where A1 and B1 tie up. What would be the call here?

AP throw in
Out of bounds by A1 since the ball was legally touched in bounds and A1 is standing out of bounds (not confident with this one just thinking out loud)

Thanks for the help