Thanks everyone for your input. The concrete wall happened to be the thing that stopped my arrow. The point is that something happened upon release and the suspect is the cracked shaft at the nock end.
Nothing interfered with the bow itself during the shot (i.e. hit a pant leg or something). I'm not a great shot but I don't miss my target by 8 feet and my bow doesn't torque the way it did on that shot!
I was curious if this had happened to someone else and what might have caused the nock end to crack if the arrow hadn't hit anything hard in its life. I was curious if a super tight fitting nock on the shaft would add stress during release and accelerate a failure.
To Wingnut's point, the shaft was probably cracked before I shot it.
Thanks again everyone!