Thousands of people have gathered in Moscow to mourn Boris Nemtsov, the most outspoken political foe of Russian President Vladimir Putin.

Chess Grand Master Garry Kasparov, a writer and political activist who's been thrown in jail twice by Putin, shared insight on Nemtsov's murder and the political climate in Russia on "Sunday Morning Futures" today.

Kasparov revealed that he knew Nemtsov for two decades and had been working closely with him since 2004.

"The man was full of life. He was fighting Putin to the last hour of his life," Kasparov said, noting that Nemtsov gave an interview just 40 minutes before he was killed in which he called Putin "the greatest mistake of the presidency."

Kasparov added that Nemtsov was about to release new report proving that Russian troops participated in the aggressive actions in Ukraine.

"We can't prove that Putin was giving an order to eliminate the most vocal critic of his regime. But the atmosphere that has been created was paranoia - the fear, the hatred - that was spread by the Russian propaganda machine 24/7," Kasparov said.

"People should realize Nemtsov was shot at a place that has more video cameras than Ft. Knox," he said, noting that a snow removal truck just happened to block the camera angle that would show the face of the killer before he made a clean getaway.

"We understand what happens with any critics of Putin's regime in Russia."

Watch more from "Sunday Morning Futures" above.