During the Portella della Ginestre sequence, a member of the Communist Party gives a speech. In reality the shooting in the massacre began before anyone had a chance to speak to deliberately stop the speech starting.
When his mother comes to view and identify his corpse, Salvatore's stomach clearly moves as the actor struggles to control his breathing.
When Savatore's mother visits him after he has been killed, you can see that the actor is visible breathing, eyelids move, and abdomen getting up and down. (About 52 minutes into the movie.)