EDISON - The FBI has many unanswered questions surrounding Monday's bomb blasts at the finish line of the Boston Marathon.

Agents want to determine whether or not the bombs were the work of one person or a group. Investigators also want to know more about who the attackers were and why they chose this act of terrorism.

News 12 New Jersey spoke to a retired senior FBI agent, who says teams of agents are already on the case. Granville Long says the key to finding those answers often lies in the details. The construction of the bombs may give investigators a place to start.

Sources have said that the bombs may have been loaded into pressure cookers and put into black duffel bags. They contained ball bearings, which became shrapnel when they were detonated.

Long says that if the shrapnel was analyzed, agents may be able to determine where it was made.

The ball bearings are just one of about 20 different areas, such as the duffel bags and other ingredients in the explosives, that will be investigated.