charging call

[readingofficial]

I had a game this weekend and was working with a much more experienced partner. We had a call that we did not agree on. I had a charge, the Defender had L.G.P. before the offensive player left the floor to take a shoot and crashed into the defender. My partner tells me it is a block, because the offensive player was in the act of shoot before the defensive had L.G.P. Can someone explain to me the proper call there. Thanks