It is my understanding that, while a train he was on was captured by rebels, the Tsar abdicated the throne. Thus, the February Revoltuion passed with little violence. But, those in power, wanting to stay in the war, caused the Bolsheviks to initiate the October Revolution, where the Romanovs were all executed.
Have I missed something?
In any case, I await your responses.
Tsar Nicholas II was not killed in October 1917, what you have missed is that after the October Revolution a civil war broke out in Russia, for various reasons, between two sides one being known as the Whites and the other the Reds (Bolsheviks)
Nicholas II was killed by the Reds during this war so he could not be captured and used as a rallying point by the Whites (my source argues this was unfounded paranoia, after 1905 and the disastrous years of WWI noone was going to rally behind Nicholas II even if he had been rescued)
Sources
A Peoples Tragedy: The Russian Revolution by Orlando Figes