A 12ft pet Burmese python broke out of an aquarium and strangled a two-year-old girl in her bedroom, police in Florida said.
Shaunia Hare was already dead when paramedics arrived at the home, said Lt Bobby Caruthers of the Sumter County Sheriff's Office.
Charles Jason Darnell, the snake's owner and the boyfriend of Shaunia's mother, discovered the snake missing from its aquarium and went to the girl's room, where he found it on the girl and bite marks on her head, Mr Caruthers said.
Mr Darnell, 32, stabbed the snake until he was able to free the child.
Authorities remained outside the house in the town of Oxford, awaiting a search warrant to remove the snake from the home.
Oxford is about 50 miles north-west of Orlando.
Mr Darnell did not have a permit for the snake, said Joy Hill, a spokeswoman with the Florida Fish and Wildlife Conservation Commission.
He has not been charged, but Mr Caruthers said investigators were looking into whether there was child neglect or if any other laws were broken.
The Humane Society of the United States said at least 12 people have been killed in the US by pet pythons since 1980, including five children.