to three or not to three

[sc/nc ref]

A few nights ago, my partners and I were discussing a play that one of them had in a game earlier in the season. A1, in the frontcourt with the ball, has his left foot in front of the 3pt line and his right foot behind the 3pt line.
He picks his left foot up. Before placing it back down, and with his right foot clearly behind the 3pt line, he elevates and shoots. The ball goes in the basket.
Is it a 3pter or a 2?
He counted it a 3. My thinking is that until the left foot actually touches behind the 3pt line that it is still a 2pt shot (thinking along the lines of "you are where you are until you get to where you are going).
What is the correct ruling?