Say, I am carrying a chainsaw towards a tree. In that case I am about to saw that tree down.
Suppose someone stops me and asks me to cut that tree.
How can I politely inform them that I am about to do that and I got that idea before they asked me and without their "advice"?
I thought of "I was about to saw that tree down", but this phrase would be appropriate if I planned to fall the tree but something prevents me to do that.