This is what apparently happened:
When officers arrived, Loxas had returned to his house, but came to the door with the baby in his arms, police said. Peters and another officer told investigators that they saw a black object in Loxas' hand. Loxas turned to go back inside when Peters, who was standing 18 feet away at the edge of the driveway, shot him in the head with his patrol rifle, police said.
*ding dong*
"Hello?" /holding baby in hands, turns to go back inside house
*dude standing 20 feet away greases him because he saw a black object on him and was reportedly told that he had threatened a neighbor with a gun*
End of story.
...you can't shoot someone for that.