The second such incident in less than a week, three persons were killed following an argument over grazing of goats in a village in Unnao district, police said today.Goats belonging to villagers of Raidas community, who are Dalits, allegedly entered the field of one Ram Naresh Singh, a Thakur, last night in Adampur Bhasi village, leading to an altercation between members of the two communities, a police spokesman said. Both groups allegedly opened fire in which three people were killed, two of whom were Dalits and one was a Thakur, while three were injured, he said. The injured have been admitted to government hospital. Senior police officials have reached the site and additional PAC force has been deployed, the spokesman added.