A brazen killing took place in an ambush. Iran’s top nuclear scientist, who American and Israeli intelligence have long charged was behind secret programs to design an atomic warhead, was shot and killed in an ambush on Friday as he was traveling in a vehicle in northern Iran, Iranian state media reported. The scientist, Mohsen Fakhrizadeh, believed to be 59, has been considered the driving force behind Iran’s nuclear weapons program for two decades, and continued to work after the main part of the effort was quietly disbanded in the early 2000s, according to American intelligence assessments and Iranian nuclear documents stolen by Israel. One American official — along with two other intelligence officials — said that Israel was behind the attack on the scientist. It was unclear how much the United States may have known about the operation in advance, but the two nations are the closest of […]