The brothers behind the Brussels terror attacks also spied on a top nuclear researcher and hoped to build a so-called "dirty bomb," an expert involved in a probe into ISIS threats told NBC News on Thursday.
Khalid and Ibrahim El Bakraoui were responsible for planting a hidden camera outside the Belgian researcher's house, according to Claude Moniquet, a French former intelligence official who was hired to investigate potential plots targeting Europe's nuclear sector.
Authorities found 10 hours of film from that camera, showing the comings and goings of a senior researcher at a Belgian nuclear center and his family, officials announced last month.
