created this. the picture of the bombs now starting to emerge is that they were deadly but crude. a federal law enforcement official with knowledge of the boston bomb investigation tells cnn the bombs were hidden in bags inside a metal pressure cooker. a law enforcement source also told cnn that it's likely but not certain that a timing device was used to detonate the bomb. emergency room doctors said they believed the bombs contained bbs and nails intended by the bomber to kill or maim as many people as possible. >> there were a variety of sharp objects that we found in their bodies, probably this bomb had multiple metallic fragments in them and we removed them. >> mike bouchard is a former top official with the bureau of alcohol, tobacco, and firearms. >> it could be a relatively simple device but that's all you need.