Israel is working with an Iranian terror group to kill Iran's nuclear scientists, U.S. officials have told NBC News. They say Israel is financing, training, and arming Iranian dissidents known as the People's Mujahedin of Iran, a group designated as terrorists by the U.S. since the 1970s, when members allegedly killed U.S. service members. They later broke with the Iranian mullahs. Five nuclear scientists have been killed since 2007, often by a motorcycle rider attaching a magnetic bomb to the scientist's car. U.S. officials say the Obama administration is aware of the assassinations. The Iranian government claims that Israeli trainers even built a replica of one scientist’s home.