'You knew right away something was really wrong'
He saw a seaplane about 300 feet in the air, emerging from behind one of the many high-rise condominiums that dot the coast of Miami Beach.
In a moment, one of the aircraft's wings was in flames, generating such heat Mr Dilella felt the warmth in his face.
"We heard an explosion, and it looked like it was going down," said Mr Dilella, a high school student from the Miami suburb of Kendall.
"And it looked like it was coming down on people. You knew right away that something was really, really wrong."
Dozens of onlookers, mostly surfers, watched as the propeller plane crashed in the water on Monday after taking off for Bimini in the Bahamas.
The plane's operator, Chalk's Ocean Airways, said 18 passengers and two crew members were on board. All 20 were killed, including three infants.
Many of the victims were returning home to the seven-mile-long Bimini island after Christmas shopping jaunts.
Within minutes of the crash, rescue crews were scouring the water, along with people on jetskis and surfboards.
Ambulances waited on land to care for survivors, but none were found.
The sands of Miami Beach were relatively busy on Monday, with many schools already closed for the holidays and the Christmas week traditionally one of the busiest for South Florida tourism.
As word of the crash spread, dozens more people rushed to the scene, which was cordoned off by yellow police tape.
And even as coast guard helicopters hovered overhead, some surfers remained in the water, only a few hundred feet away from rescue crews searching for survivors.
Mr Dilella said he could see at least 300 surfers along the beach when the plane crashed, and some of them frantically tried to rush toward the spot where the small craft hit the water.
Surfer Maurice D'Giovianni, 42, said he heard a distinct "boom" before a wing fell off and the aircraft tumbled into the water, with black plumes of flame tailing it.
"It exploded in the air, and one of the wings flew out of there," he said.
"The other part of the plane was on fire, and it just went straight down."
As soon as he saw the crash, "I said right away, 'I think those people are dead'."
Federal investigators are still searching for evidence to explain why the seaplane broke apart.
Acting National Transportation Safety Board (NTSB) chairman Mark Rosenker said that investigators hope to find the cockpit voice recorder to see if it provides any clues to why the 58-year-old Chalk's Ocean Airways plane crashed moments after taking off.
The plane had no flight data recorder.
Much of the wreckage, including the main fuselage, was expected to be raised from about 35 feet of water.
Nineteen bodies had been recovered; the 20th was still missing, Mr Rosenker said.
He told reporters investigators would look into all possible causes and urged witnesses who made amateur video or photos of the crash to come forward.
A coast guard security video will also be reviewed.
But he said most of the answers would come from examining the wreckage, in the channel called Government Cut that is used by cruise ships and freighters, and said the investigation could take a year.
One amateur video obtained by CNN showed the main part of the aircraft slamming into the water followed by a flaming object that was trailing thick black smoke.
Petty Officer Ryan Doss said the coast guard video, which wasn't being made public, didn't capture as much as the CNN video.
"You see the plane taking off and it goes off into the distance. Then you see smoke," he said.
The seaplane - a twin-engine Grumman G-73T Turbine Mallard - was built in 1947.
FBI officials said there was no immediate indication of terrorism or criminal intent.
Coast guard spokesman Dana Warr also saw the plane take off and then heard the crash.
"I saw the aircraft take off like it does every other time," he said.
"I didn't think anything of it when I saw the black smoke from the pier, until I then heard the coast guard alarms go off."
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