T.C.
My nephew was doing the same thing at two years old -- actually, taking off his diaper and pooping on the floor. She has started looking into potty training him and so far, things are working out.
Is he pulling off his diaper to then poop? Maybe then he is ready to potty train...
I'd probably touch base with his pediatrician and inquire about it. I'd be careful about disciplining him on pulling off his diaper, especially with the poop involved, as he might be trying to tell you something.
Good luck!
T. :)