Taylor Soper shared the video Wednesday from Murrells Inlet, showing the massive reptile eating the other gator whole.
Soper said the video was taken from his parents' backyard, and told Storyful the smaller gator was at least six feet long.
"The small one getting eaten... was eating an even smaller one last week!" Soper wrote.
It's not unusual for alligators to eat large prey such as deer, bears and even other gators.
According to the Key West Aquarium, if a gator has caught something too large to eat in one bite, it will drown it by violently spinning it in the water in a move commonly called a "death roll."
Afterward, it will store the dead prey to allow for decomposition and easier consumption.
Storyful contributed to this report.