It is a gloss over step tbh but yes people die. Revolutions are not a tea party. It doesn't have to be a lot though. The Bolsheviks barely had to kill anyone to achieve state power. Granted they threatened the provisional government with shelling but after the first few shells they capitulated. Most of the seizure of power comes before officially "taking" the state by controlling or subverting its institutions. You first deprive the state of its power before you point the guns at its officials.

They won't relent unless you at least point the guns at them to be clear. The provisional government in Russia famously held on to an utterly hopeless situation for "historical posterity". They wanted to at least look like they held out to the last.

Proletarian revolutions don't have to be, and often aren't, the chaotic violence in the streets that people imagine. Through a strong vanguard party the violence of revolution can be directed and restrained.

This isn't to say people aren't going to die. Unfortunately the dying usually comes in the counter-revolution/civil-war that follows. These are messy things and I personally don't think anyone "wants" revolution. Revolution is something people do because their current circumstances have become utterly intolerable and all other avenues have been tried. The vanguard party does exist to creat revolution it exists to steer it away from the common ruin of all contending classes. Violence is nevertheless, an inevitable outcome.

Edit: right, as for trying them for their crimes. Yeah some of the war-criminals deserve to die. They are responsible for mass murder.