Boston bombers 'motivated by radical Islam but unconnected to Muslim terrorists groups' US officials say it appears Dzhokhar and Tamerlan Tsarnaev acted alone when they allegedly planted the Boston Marathon bombs Acted alone? Officials believe the Tsarnaev brothers are unconnected to Muslim terrorist groups The Boston bombers appear to have been motivated by a radical brand of Islam but do not seem to be connected to any Muslim terrorist groups, US officials have said.Dzhokhar Tsarnaev, 19, was charged with using a weapon of mass destruction as he lay handcuffed to his hospital bed yesterday.The teenager is in a serious but stable condition in the Beth Israel Deaconess Medical Centre where he is unable to speak after apparently shooting himself in the throat.It is thought the teenager placed a gun in his mouth and pulled the trigger in a desperate bid to avoid capture and a possible death penalty.His older brother and fellow suspect Tamerlan, 26, was killed during a fier