The report said the girl was up in the tree screaming. As the deputy tried to get a better look, he heard a hissing sound and saw the alligator in the water at the base of the tree.
Deputies said the Lake County Marine Units were still about 20 minutes away and the girl couldn't hang on to the tree much longer.
According to a report, the deputy was about 4 feet from the alligator and was hoping his presence would scare it away, but instead, the alligator got closer.
The deputy fired a single .223 round from a Bushmaster AR15, killing the reptile.
Lake County marine biologists came to the scene to search for the alligator’s body.
The girl was not injured.