Caesar wasn't murdered by the government, he was murdered by a small group of conspirators within the state. That's not the same thing at all. The conspirators guarded their plot jealously--though many knew that something was up, few were let in on what exactly the secret was. Cicero, for example, tried to get in on the plot through his friend Brutus, but was deemed untrustworthy and excluded. And Caesar's murder resulted in a sharp division among the members of the state. Many declared the support for the murderers, but to others Caesar's murder was a gross breach of law and custom--and this is an attitude not just held by Caesarians. Then there were those who had no real sides, as Dolabella's (rather self-serving) defection to Antony's camp from Brutus' shows.

The murder was known the moment that it happened. Caesar was murdered in a public place, the Theater of Pompey where the senate was meeting, and in front of a crowd of senators, who according to Plutarch fled in terror. The conspirators, as Liberatores and tyrannicides, walked calmly from the Theater of Pompey (which is down near the Tiber) up to the Capitol, openly declaring what they had done. The reaction of the Roman state and the Roman people was mixed. Some, such as Gaius Octavius and Lentulus Spinther who joined in the procession to the Capitol despite not having been in on the conspiracy, were quite open in their support of the murder, whereas the Caesarians and a great many ordinary senators and people were appalled. Antony, as sole consul, was able to get a general amnesty passed for the murderers in exchange for recognition of the inviolability of Caesar's legislation, thus reconciling the two factions. But he soon overturned this when in the next couple days he delivered Caesar's funeral oration and stirred up a mob attack on the murderers, burning some of their homes to the ground and forcing the rest to flee--this is the entire reason that the second round of civil wars began and why the Caesarians fought the Republicans and Philippi. The Romans didn't react to this as a collective entity, there were thousands of individual opinions, Caesar's murder was quite possibly the most important event in around a decade for the Roman state