Alexander Barmine, a Soviet defector who knew both Stalin and Kirov, asserted that Stalin arranged the murder with the Soviet secret police, the NKVD, who armed Nikolayev and sent him to assassinate Kirov. Author and Marxist scholar Boris Nikolaevsky argued: "One thing is certain: the only man who profited by the Kirov assassination was Stalin." Nikita Khrushchev, in his controversial Secret Speech in 1956, said that the murder of Kirov was organized by NKVD agents. Khrushchev noted that the NKVD agents tasked with protecting Kirov were eventually shot in 1937, and assumed that this was to "cover the traces of the organisers of Kirov's killing".