The father and the alleged abuser apparently knew each other, according to Lavaca County Sheriff Micah Harmon.
Neither man has yet been identified.
The 4-year-old has been left inside the family’s house during a social gathering on Saturday while other members of the family were tending to horses, according to CNN.
The father returned to his house, caught the man in the act, and began striking him in the head repeatedly, Harmon said.
The man was pronounced dead on the scene, while the daughter was taken to a local hospital to be examined.
Harmon said the girl was “OK besides the obvious mental trauma.”
Asked whether they would press charges against the father, the sheriff replied, “You have a right to defend your daughter. He acted in defense of his third person. Once the investigation is completed we will submit it to the district attorney who then submits it to the grand jury, who will decide if they will indict him.”
Harmon said the father was “very remorseful,” adding that he didn’t know the man was going to die.
Authorities are withholding the dead man’s name while they notify his next of kin.