From an article by John F. Andrews in the October issue of The Atlantic:

If you're like a lot of Americans, your school days included a class in which you recited orations from Julius Caesar. You may have been taught that the title character in Shakespeare's tragedy was a forerunner of the king that Britain's New World colonies felt driven to defy in 1776. And you may have learned that the Patrick Henrys and Nathan Hales who took arms against George III were following in the steps of honorable patriots who had done what they'd had to do during the most soul-trying days of republican Rome . . .

Like the Marcus Junius Brutus of Shakespeare's play, John Wilkes Booth was keenly receptive to the promptings of ancestral tradition. He aspired to what "an antique Roman" would do in his place, and it is very likely that he was alluding to {this} when he spat out "Sic semper tyrannis" ("Thus be it ever to tyrants") and slew a president he had frequently scorned as a "king."

What Booth declaimed was the motto of the state of Virginia. For him it was a rallying cry for the Confederacy. But it also seems to have epitomized a cause he identified with "the noblest Roman of them all."

. . . Like the Brutus of Shakespeare's play, John Wilkes Booth assumed that his act would be gratefully applauded; and like his role model, he was astonished by the hostility it elicited among a public whose sympathy for the fallen leader he had grievously underestimated. Near the end he wrote in his diary, "After being hunted like a dog . . . with every man's hand against me, I am here in deep despair. And why? For doing what Brutus was honored for. What made Tell a hero."