Lavaca County Sheriff Micah Harmon said the 23-year-old father, whose name has not been released, is unlikely to be arrested for Saturday's killing and that no evidence so far has led investigators to doubt his story.
"There doesn't appear to be any reason other than what he told us," Harmon said.
Harmon said the victim was a 47-year-old man from Gonazles with no apparent prior criminal history. His name continued to be withheld Monday because authorities still hadn't tracked down any of his family.
The victim was an "acquaintance" of the father who had come to help care for some horses, Harmon said. He did not know how long the two men may have known each other. The girl was taken to a hospital to be examined and has since been released, Harmon said.
The father called police late Saturday afternoon and told them he attacked a man caught trying to sexually assault his daughter, Harmon said. The alleged attack happened near a barn where some horses were being kept.
"So when he heard the screaming and he ran out there to see what was wrong with his daughter," Harmon said.
The sheriff says her underwear had been removed and that her father hit the man's head with his fist, killing him.
No one in Shiner is second-guessing his actions.
"A couple friends of mine, we're sitting right there and we discussed what little we knew about it and I frankly said, I'd give the guy a medal," one man told Eyewitness News.
"When he saw that, I think it's justified. I'm sorry but I totally think it's justified. What would you do if it's your child?" another Shiner resident said.
Harmon said the father appeared to be remorseful over the man's death and said he never intended to kill him, but rather save his child. A grand jury will decide what, if any, charges the father will face.
The victim's body was sent to the Travis County medical examiner for an autopsy.
The ranch near Shiner is about 130 miles east of Houston. Killings are rare in rural Lavaca County. Harmon said his office has only investigated six since in his eight years as sheriff.
The Associated Press contributed to this report.
