Julius Ceaser was a military man that was very rich. He had taken out his great enemies and had become council. He had become the highest person in Rome in 44BC.
His power and high ranking in Rome caused conspirators to plan and kill Ceaser, including his Brutus his close friend. Brutus was persuaded by the other conspirators to to kill the person who spared him. That was a great act of betrayal.
The conspirators killed Ceaser and locked themselves into the capital. Rome had went into panic after the assignation because of the death of their ruler, which they appraised.