WARNING: The following details may be disturbing to some readers.

New details of the fatal alligator attack have been revealed through the release of the 911 call of a neighbour who witnessed the 85-year-old being taken into a Florida lake on Monday.

The neighbour says she was watching the woman walk her dog by the canal of the Spanish Lakes Fairway near Fort Pierce, Fla., when the 3.3-metre alligator attacked the dog.

“I just happened to look out my bedroom window and saw her," she said to the 911 operator. "She was walking her little dog, and the gator grabbed the dog, and she fell down and (it) took her.”

The neighbour can be heard frantically screaming and repeatedly saying "oh my God" as she explains how she attempted to help the woman but it was too late.

"She was swimming towards me, I said, 'Come to the bank.' I was trying to stick a pole out for her and I was calling you [911] at the same time and she's gone, she's gone," she said.

Additionally, she said she saw the alligator swimming in the area within the last few days but it had been on the further side of the lake.

The dog was found by the neighbour and she was able to bring it into her home as she waited for emergency services to arrive.

At the end of the call the neighbour described seeing the woman's body emerging from the water but saying repeatedly "she's gone."

The alligator has since been euthanized.

With files from the Associated Press.