The three leaders [triumviri] Octavian, Lepidus, and Anthony ordered his execution. But it was Anthony who hated him most.
This is how the Roman historian Appian tells it:
“Cicero…was condemned along with his son, his brother, his nephew, and all his connections, supporters, and friends.
He was escaping by boat but being unable to tolerate the roughness of the sea, returned to land and lay low in a country place of his…near the Italian town of Caieta. When the men who were tracking him down came near…some crows flew into his room, squawking and rousing him from sleep, and pulling his bedclothes from him, until his attendants divined that this was a sign from the gods, put him in a litter, and took him down to the sea again through a dense thicket which hid him.
“Numbers of men were running in various directions and trying to discover if Cicero had been seen anywhere. Everyone else, wishing Cicero well and pitying him, said that he had already put out to sea and his boat was under way, but a cobbler, who was a dependant of Clodius, one of Cicero’s bitterest enemies, showed the path to a small party under Laenas, the officer in command. He ran along it, and when he saw that Cicero’s attendants far outnumbered the men coming with him to wreak their vengeance, he very astutely shouted out, “Centurions behind me, come up on the double!’
“The attendants were terror-struck, thinking that more soldiers were coming, and Laenas, who had actually once won a court case with Cicero’s support, pulled his head out of the litter and proceeded to cut it off. It took three blows and some sawing through because of his inexperience, and he also cut off the hand with which Cicero had composed the speeches against Anthony, portraying him as a despot, which he entitled Philippics in imitation of Demosthenes.
“People immediately rushed to take the good news to Anthony, some on horseback, others by sea. Laenas found him seated in the forum and waved the head and hand at him from a long way away. Anthony was overjoyed and garlanded the officer, and gave him 250,000 denarii on top of the normal reward, on the grounds that he had removed the man who had been his greatest and most aggressive personal enemy.
“Cicero’s head and hand were fastened for a long time to the rostra in the forum, where he had previously played the popular leader, and more came to see the sight than had listened to him. It is said that Anthony had the head placed before the table at his meals, until he was sated with looking at the vile object.
“This, then, was the way in which Cicero was killed and outraged after his death—a man who is renowned to this day for his literary achievements, and was of the greatest service to his country when he held the office of a consul.” Appian, The Civil Wars, Book IV
Compare with Plutarch’s account.