Final answer:
After declaring himself dictator for life, Julius Caesar was assassinated by a group of senators. His heir, Octavian, became the first Roman Emperor.
Step-by-step explanation:
After Julius Caesar declared himself dictator for life, he was assassinated by a group of senators who resented his power and wanted to save the Republic. This event marked a new chapter in the Caesarian dictatorship. However, it was Caesar's heir, Octavian, who became the first Roman Emperor, not Caesar himself. Octavian, later known as Augustus, took the reins of power after Caesar's death and established the Roman Empire.