They were all Baptist churches in the same county, so it was somebody who doesn't like Christians perhaps (that could be any Daily Kos/DUmmy, or muslims) or somebody with a specific thing about Baptists. Also, it's probably somebody local who knew the location of all the churches and planned out the quickest route from church to church.
Some lunatic will be on the Internet bragging about this. It'd be interesting to see the buzz over on DU about this, but I don't think I could stomach that this early in the morning.
More than likely just some mentally disturbed person or stupid juveniles living in the area.