Livy, Periochae 116-120
Titus Livius or Livy (59 BCE - 17 CE): Roman historian, author of the authorized version of the history of the Roman republic.
A large part of Livy's History of Rome since the Foundation is now lost, but fortunately we have an excerpt, called the Periochae, which helps us reconstruct the general scope. This translation was made by Jona Lendering.
From Book 116 (which is the eighth dealing with the civil war)
[116.1] [45 BCE] Caesar celebrated a fifth triumph, for his Spanish victory.
[116.2]  After the Senate decreed many of the highest honors (such as the right to be called "father of the fatherland" together with an eternal inviolability and dictatorship), several grudges rose against him: because he did not rise from his throne in front of the temple of Venus Genetrix when the senators arrived to present him with these honors; because, when his fellow consul Mark Antony, dancing with the luperci, placed a diadem on his head, he placed it on his throne; and because he expelled the tribunes of the plebs Epidius Marullus and Caesetius Flavus from office after they had caused hostility towards him, arguing that he was aiming at one man rule.
[116.3] For these reasons, a conspiracy was formed against him, its leaders being Marcus Brutus and Gaius Cassius, and, from Caesar's own men, Decimus Brutus and Gaius Trebonius. With twenty-three stabs he was murdered in the Curia Pompeia, and the Capitol was occupied by the assassins.
[116.4] The Senate decreed an amnesty for the murder, and when the besieged conspirators had received the children of Antony and Lepidus as hostages, they descended from the Capitol.
[116.5] By Caesar's will, Gaius Octavius, the grandson of his sister, was adopted as his son and made heir to half his estate.
[116.6] When Caesar's corpse was brought to the field of Mars, it was burned in front of the Speaker's platform by the plebs.
[116.7] The office of dictator was banned forever.
[116.8] One Chamiates, a man of the lowest rank, pretending to be the son of Gaius Marius, caused disturbances among the credulous plebs, but was killed.
From Book 117
[117.1] Gaius Octavius arrived from Epirus (he had been sent there in advance by Caesar to wage war in Macedonia), and after all kind of favorable signs, he accepted the name of Caesar.
[117.2] In an atmosphere of confusion and disturbance, Marcus Lepidus accepted the office of pontifex maximus.
[117.3] The consul Mark Antony recklessly tried to dominate the stage and carried a law concerning changes in the assignment of provinces by violence. He intensely hurt Caesar, who came to ask for help against the assassins of his great-uncle. As a result, Caesar started to acquire resources against him in the colonies of the veterans, which he would use for himself and the republic.
[117.4] The Fourth and the Martian legions indeed transferred their loyalty from Antony to Caesar, and because of the savage behavior of Mark Antony (who killed several suspects in his camp) others followed.
[117.5] With an army, Decimus Brutus occupied Modena, in order to head off Antony, who was making for Cisalpine Gaul.
[117.6] Itnote[Book 117.] also contains an account of the scattering of men on both sides to take over provinces, and describes other preparations for war.
From Book 118
[118.1] In Greece, Marcus Brutus, pretending to act for the benefit of the state and the campaign against Mark Antony that was undertaken, obtained the army of Publius Vatinius and the province as well.
[118.2] The Senate gave Gaius Caesar, who as a private citizen had built an army, the powers of a propraetor and the ornaments of a consul, and promised that he would be made senator.
[118.3] Mark Antony besieged Decimus Brutus at Modena, and the envoys sent by the Senate to negotiate peace were unsuccessful,
[118.4] so the Roman people accepted the military dress.
[118.5] In Epirus, Marcus Brutus overcame praetor Gaius Antonius and his army.
From Book 119
[119.1] By the treachery of Publius Dolabella, Gaius Trebonius was murdered in Asia.
[119.2] Because of this crime, Dolabella was declared to be an enemy by the Senate.
[119.3]  After consul Pansa had unsuccessfully fought against Antony, consul Aulus Hirtius arrived with his army, defeated the troops of Mark Antony and brought the fortunes of both sides in balance again.
[119.4] Antony, defeated by Hirtius and Caesar fled to Gaul, where he joined Marcus Lepidus and the legions under his command; the Senate declared him and every soldier in his army an enemy.
[119.5] Aulus Hirtius, who had been killed in the camp of the enemy after his victory, and Gaius Pansa, who had died from wounds received during his defeat, were buried on the Field of Mars.
[119.6] The Senate was hardly grateful to Gaius Caesar, who was the only one of three leaders to survive: it voted the honor of a triumph to Decimus Brutus, who had been freed from the siege of Modena by Caesar, and made no satisfying reference to Caesar and his soldiers.
[119.7] Therefore, Gaius Caesar, on advise by Marcus Lepidus, reconciled himself with Mark Antony, marched on Rome with his army, and, surprising everyone who was against him, was made consul at the age of nineteen.
From Book 120
[120.1] As consul, Gaius Caesar carried a law to prosecute those who had been involved in the murder of his father Caesar; under the terms of this law, Marcus Brutus, Gaius Cassius, and Decimus Brutus were condemned in their absence.
[120.2] Asinius Pollio and Munatius Plancus as well joined Mark Antony with their armies and made him stronger; and Decimus Brutus, whom the Senate had ordered Antony to pursue, was deserted by his legions, fled, and was put to death by Antony, into whose power he had come, by a Sequanian named Capenus.
[120.3] Gaius Caesar made his peace with Antony and Lepidus. For five years, they were to be triumvirs for the restoration of the republic, and opponents of Lepidus, Antony and Caesar were to be proscribed.
[120.4] Many Roman knights, and the names of 130 senators, were listed, such as Lucius [Aemilius] Paulus (Marcus Lepidus' brother), Lucius Caesar (an uncle of Antony), and Marcus [Tullius] Cicero.
[120.5] He was killed by Popillius, a legionary soldier, at the age of sixty-theee. His head and right hand were exposed on the Speaker's platform.
[120.6] Itnote[Book 120.] also contains an account of Marcus Brutus' acts in Greece.