Hippocrates was the son of a man named Pantares (once a victor of the Olympic Games) and the brother of Cleander. The latter, employing a mercenary army of native Sicilians, made himself tyrant of Gela in 505, the same year that witnessed the victory of the tyrant Aristodemus of Cumae over an Etruscan army at Aricia, which resulted in the final liberation of Rome from its detested king Tarquinius Superbus. Cleander ruled for about seven years, but was assassinated in 498.
Now, it was his brother Hippocrates' turn to become tyrant. He was supported by the same native mercenaries and Gelon, the commander of the cavalry. Not unlike Phalaris of Acragas, who subdued several other towns and added them to his own city-state, Hippocrates embarked upon an aggressive foreign policy, and brought several other cities under his control. For example, Leontini and Naxus, in the northwest, were conquered. He also intervened in Zancle, modern Messina.
In other words, he controlled the entire east of Sicily, except for Syracuse. In 492/491, he besieged this city, defeated the Syracusans at the river Helorus, and only left Syracusan territory when the city had given up the town of Camarina, to the southeast of Gela.
One year later, during the siege of Hybla, he was killed. His adjutant Gelon succeeded him.
In the subject towns, Hippocrates installed other tyrants. Depending on one's definition of a state, one may call his empire a great territorial state or a network of unequal alliances with vassal tyrants. However one wishes to interpret this, it was something new.