This ain't Beavis and Butthead. It's a well-trained, extremely meticulous and well-planned group who've probably cased out each of these locations over the past year, determined their escape routes, and went about the business of purchasing/procuring large, white, nondescript vehicles that can blend into a crowd with relative ease. If the killer(s) actually used a large, white truck, that would not appear to be well planned and meticulous. If fact it would appear as rather stupid.