There wasn't much that anybody could have done.
That's the opinion expressed by Zeke Miller, writing for TIME, who says the accused bombers were very difficult for law enforcement to track before the April 15 bombing.
The accused, brothers Tamerlan and Dzhokhar Tsarnaev, allegedly constructed bombs using materials that are difficult or impossible for the FBI or other law enforcement agencies to track. The bombs used in the Boston Marathon bombing were made of black powder from fireworks, nails and pressure cookers, none of which are on any law enforcement list.
While the Tsarnaev brothers were on the radar of the intelligence community, there was no way law enforcement could have caught them, Miller writes.
See the story at Time.com.