Complex sentence: Cecilio Chi, the Maya leader of Tepich, along with Jacinto Pat attacked Tepich on 30 July 1847, in reaction to the indiscriminate massacre of Mayas, Chi ordered that all the non-Maya population be killed.
Split into simpler sentences: Cecilio Chi, the Maya leader of Tepich, with Jacinto Pat attacked Tepich on 30 July 1847. In reaction to the indiscriminate massacre of Mayas that had taken place, Chi ordered that all the non-Maya population be killed.