This question was inspired by I'M GERMAN IRISH postulating that Michael deliberately killed Sollozzo first and McCluskey next was because Michael had a greater hate for McCluskey, and wanted him to suffer for that second or so in knowing that he was about to die.

Altho that may have been Michael's intention, I don't think that that's what would've occured to McCluskey as he watched Michael shoot Sollozzo.

The idea, as Tom pointed out to Michael, of killing a NYC Police Captain was so absolutley outrageous and unheard of - and surely McCluskey knew this - that I doubt if he believed during that one second that Michael intended to kill him as well.

If McCluskey were smart, and had enough time to analyze the situation, he would have realized that Michael's only chance for escape rested with killing him also, but he didn't have the time to think it through.

Instead, I imagine that his thoughts were running somewhere along the line of "Look at that dumb Guinea kid. He just killed Sollozzo..."