Boris Nemtsov had to be killed, but not only because he was going to lead an anti-war parade — that would have had at the most 16,000 people in my view, given the remote location, the problems in preparing it, the arrest of Nemtsov for the two weeks before it, etc. And not only because he was going to release a report on the war — lots of people have done that, and more can always be done, but his contribution would have been to make it interesting, viral in Russia, and compelling to foreigners. He had already done a video with a million views about MH17, with Leonid Martynyuk.
I think the reason Boris would have to be killed was because he would have easily gotten the 100,000 signatures that any candidate for president in emergency elections after the demise/withdrawal/death/overthrow of the existing president needs to have. This is what Robert Coalson helpfully explained at RFE/RL. It's actually easier to run for president after a death/overthrow like that then in the normal course of things (it seems to me). Why did they have to do this? Because they had nothing to imprison him on.
http://3dblogger.typepad.com/minding_russia/2015/03/what-i-think-is-going-on-in-moscow.html
This is a very interesting remark.
Putin’s Airforce 1 just landed in St Pete http://www.flightradar24.com/data/airplanes/ra-64521/#5c3781d …
Nemtsove was killed to start the Moscow Maidan.