"Get out, get out" screamed onlookers to the boy swimming in the Dead River in central Florida, after spotting the 10-foot alligator lurking nearby.
But it was too late.
Police eventually recovered Brian Griffin's body and rushed him to a nearby hospital where he was pronounced dead.
Deputies and witnesses saw the alligator surface at least once with the boy in his jaws, but the animal quickly disappeared across the river, the Orlando Sentinel reported in a story for Thursday editions.
The boy was under for at least 25 minutes before a sheriff's helicopter spotted him and dropped a buoy to guide deputies, who pulled him up.
"We saw gators all day," said 14-year-old Justin VanGorder, who said he was swimming with Brian. "Every time we saw them, we would get out of the water."
Justin said he and the other boy saw alligators and got out of the water, but Brian wouldn't get out.
Investigators dimmed the lights around the marina and said they were going to shoot any alligators they could find. Several shots rang out Wednesday night, but no gators were killed.
Authorities said complaints about alligators have increased because so many are turning up around rain-bloated retention ponds, ditches and canals.
Florida has had 12 other fatal alligator attacks since the state began keeping track in 1948. The most recent came in September 2001, when an 81-year-old man bled to death after his leg was bitten off below the knee.