What on earth is going on in his mind during such encounters?
I think you're back to 1984 again:
There will be no curiosity, no enjoyment of the process of life. All competing pleasures will be destroyed. But always—do not forget this, Winston—always there will be the intoxication of power, constantly increasing and constantly growing subtler. Always, at every moment, there will be the thrill of victory, the sensation of trampling on an enemy who is helpless. If you want a picture of the future, imagine a boot stamping on a human face—forever.
Power is not a means; it is an end. One does not establish a dictatorship in order to safeguard a revolution; one makes the revolution in order to establish the dictatorship. The object of persecution is persecution. The object of torture is torture. The object of power is power.