Stabbing an armed FBI agent with a knife sounds like a strategy for accomplishing the well-known "suicide by cop," in this instance the variant "suicide by FBI agent." I hope the FBI agent who was stabbed is okay.
If that is the case, all that is lost is the possibility of extracting addition intelligence about further members of the Boston marathon bomber terrorist cell. On the upside, the state saves hundreds of thousands of dollars in trial and incarceration costs. See the ABC News article for details.
