Stalin often gave conflicting signals regarding state repression. In May 1933, he released from prison many convicted of minor offenses, ordering the security services not to enact further mass arrests and deportations. In September 1934, he launched a commission to investigate false imprisonments; that same month he called for the execution of workers at the Stalin Metallurgical Factory accused of spying for Japan. This mixed approach began to change in December 1934, after prominent party member Sergey Kirov was murdered. After the murder, Stalin became increasingly concerned by the threat of assassination, improved his personal security, and rarely went out in public. State repression intensified after Kirov's death; Stalin instigated this, reflecting his prioritisation of security above other considerations. Stalin issued a decree establishing NKVD troikas which could mete out rulings without involving the courts. In 1935, he ordered the NKVD to expel suspected counter-revolutionaries from urban areas; in early 1935, over 11,000 were expelled from Leningrad. In 1936, Nikolai Yezhov became head of the NKVD.