Dzhokhar Tsarnaev is accused of using explosives-filled pressure cookers as bombs . The FBI says the brothers used a homemade explosive device to carry out their Boston Marathon bombing on April 15, killing three people and injuring more than 260 others. Read more : Japan fires military chief over WWII denial . The term `` WMD '' is often used to refer to nuclear , biological and chemical arms .
Dzhokhar Tsarnaev is accused of using explosives-filled pressure cookers as bombs . The FBI says the brothers used a homemade explosive device to carry out their Boston Marathon bombing on April 15, killing three people and injuring more than 260 others. The term `` WMD '' is often used to refer to nuclear , biological and chemical arms .