The son of Tarqunius Priscus, Tarquinius Superbus (Tarquin The Arrogant) came to the throne in a violent way, having killed his predecessor Servius Tullius. He also had no true authority to rule Rome, since neither had the people elected him nor the senate ratified him. (The same was true for Servius Tullius, but he overcame this by slowly assuming the kingship.) Because of his tenuous hold upon the throne, Tarquin set about ruling with fear.
His first act as king was to refuse burial for Servius Tullius, saying that Romulus' body had not been buried either. Then he sentenced to death all of the senators, who had supported Servius just before his death. Anyone Tarquin even suspected of treason would be sentenced to death, and their property seized by him.
Tarquin was just as brutal in his foreign affairs. In his dealings with the Latins, one king showed him disrespect when Tarquin showed up late to a conference. Tarquin then had him framed for attempted murder, then as punishment bound him to a stone and tossed him into the water.
While fighting the neighboring town of Gabii, Tarquin encountered difficulties taking the town. He therefore sent his youngest son Sextus to the town, acting as if he was forced to flee from his father. Since he had intimate knowledge of Rome and her king, the Gabii gladly received him. Eventually, Sextus worked his way up to be general of their army. He won many minor battles against the Romans, and soon was the most powerful man in the city. Sextus then set about killing every leader of the Gabii, and then handed the town to Tarquin without a fight.
When Tarquin was not fighting, he was busy improving Rome with major building projects. By always keeping the people busy, they had little time to worry about revolt. He brought in trained engineers from Etruria, and employed the masses as his laborers.
He continued the work of building the Temple of Jupiter on a lavish scale. He also had excavated the huge Cloaca Maxima, or 'Very Big Ditch.' This was the main sewer of Rome, which eventually drained into the Tiber River.
Tarquin needed more money to continue his massive building projects. He therefore decided to attack the wealthy town of Ardea. The initial assault of the town was unsuccessful, and so the army settled in for a long siege.
One night during the siege, Sextus and his cousin Collatinus got into an argument about whose wife was better. Someone got the idea to simply go to each man's house and see what their wives were doing. The men were all drunk, and this sounded like a good idea. In Rome, they found Sextus' wife at a party. Collatinus' beautiful wife Lucretia was busy at home with housework. Collatinus had clearly won the argument, and Sextus became enamored with Lucretia. The next night, Sextus returned to Rome and raped Lucretia.
Lucretia summoned her father and Collatinus, who returned with his friend Brutus. She told them what Sextus had done, and made them promise to seek revenge. Then, she took out a knife and stabbed herself in the heart. Brutus withdrew the knife from her lifeless body, and made the other men present swear that they would overthrow Tarquinius Superbus, and that there should never again be a king of Rome.
The men carried Lucretia's body out into the square for all to see. Then Brutus cried out that it was time to act against their king. Leaving others in charge of Rome, Brutus then marched out to lead the army into revolt. Meanwhile, Tarquin himself was returning from the army to quell the revolt in Rome. Brutus avoided him, and continued onto the army, who welcomed him and the revolution. When Tarquin arrived at the city, he found the gates were shut and the people firmly against him. With neither the town nor an army, Tarquin was forced to flee with his family (only Sextus did not accompany him) to Etruria.
Livy. Ab Urbe Condita.