US authorities say a father who caught a man sexually assaulting his four-year-old daughter and beat him to death may not face charges.



The father, from Texas, punched the man repeatedly in the head, killing him, Lavaca County Sheriff Micah Harmon said.



The girl had been left inside the family's house during a social gathering on Saturday while other members of her family were tending to horses, Sheriff Harmon told CNN.



He said the father returned to the house and caught the man abusing his daughter before unleashing his attack. The man was pronounced dead at the scene.



The girl was taken to a local hospital for examination before being released and was "OK besides the obvious mental trauma," Harmon said.



He said the father was ''very remorseful'' and did not know the other man was going to die.



"You have a right to defend your daughter," Harmon said after being asked whether police would press charges against the girl's father.



''He acted in defence of [of her]. 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.''



Neither man has been publicly identified.

- Sydney Morning Herald