?

Boston's police commissioner says the Boston Marathon bombing suspects were likely planning other attacks. Investigators reached the conclusion based on the cache of weapons uncovered.

Boston authorities found an arsenal of homemade explosives after Friday's gun battle between police and the two suspects. One improvised explosive device was found in the Mercedes the brothers are accused of carjacking.

The older Tsarnaev brother Tamerlan died in the gun battle. The younger one, Dzhokhar, remains in serious condition under heavy guard. It is not clear when he will talk and what he will tell. The most serious charge would be the use of a weapon of mass destruction to kill people.

This carries a possible death sentence. Surveillance video from Monday's attack shows Dzhokhar Tsarnaev dropping his backpack and calmly walking away before the bomb exploded.