The death of Ceasar. He ignores the soothsayers' final warning. Ceasar denies the pardon of one of the conspirator's brothers. They assassinate him with Brutus stabbing him last.
This scene is the funeral of Ceasar. Brutus speaks and defends his group saying Ceasar was too ambitious and a tyrant. Mark Antony, after not being killed, persuasively speaks and says Ceasar's will. This convinces the crowd that the conspirators should be killed and starts a riot. Mark Antony enlists the help from Octavius and Lepidus.
This act is focused on the death of a poet, Cinna. He had the same name as a conspirator, so the mob killed him. This is the start of the riot.