I always saw it as Vito,wanting to get through everybody on the list as quick as possible,so he could then go and enjoy his daughters wedding.The tone in Vito's voice,seems to sound impatient,rather than fear.

The hero and the coward both feel the same thing, but the hero uses his fear, projects it onto his opponent, while the coward runs. It's the same thing, fear, but it's what you do with it that matters. Cus D'Amato