Boris Nemtsov was assassinated on February 27, 2015, close to the Walls of the Kremlin in Moscow ! Vladimir Putin vowed that his killers would be found and prosecuted.
Shortly afterwards Chechen suspects were arrested, but since then speculation has involved other people.
This is not the first time that out-spoken critics have suddenly been "eliminated" in Russia, or even when they were abroad.
Nemtsov was a politician and well known in Russia. When Boris Eltsin was President he was even First Deputy Prime Minister. However, when Putin became President, he became the Leader of the Opposition and critical of the totalitarian style of leadership which Putin was introducing.
Once again in Russia it seems an assassination will be forgotten as time goes by, or until the next one is reported !