SOUTHWEST MIAMI-DADE (CBS4) – The National Transportation Safety Board and the Miami-Dade Police Department’s Homicide Bureau are investigating a deadly helicopter crash in a Southwest Miami-Dade parking lot.

Two men on board the aircraft were pronounced dead at the scene, an NTSB investigator said Wednesday night.

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Detectives were withholding the names of the victims pending next of kin notification.

Investigators confirm the helicopter, a Robinson R44 owned an operated by Bravo Helicopters of Miami, had taken off from Tamiami Airport shortly before it crashed about 2 miles away near SW 122 Ave. and SW 128 St. at about 4 o’clock Wednesday afternoon.

Witnesses could be heard screaming for help in the terrifying moments following the crash.

Some watched in horror with their cell phone cameras rolling, while others jumped into action.

“Some people grabbed the fire extinguishers from the gym and other places and started turning off the fire,” Julia Senior told CBS 4’s Lauren Pastrana. “I just ran inside and started crying.”

Senior runs a gym just feet from where the aircraft went down.

“I feel pieces falling down,” she said. “Thirty seconds after that, right in front of me, the helicopter crashes right in top of the palm tree.”

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William Barraga sells hotdogs along SW 128 Ave. He said it sounded like the helicopter was having engine problems before it went down.

“You hear thump, thump, thump, thump, thump. I’m selling a hot dog and I seen the thing explode,” Barraga explained.

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Miami-Dade Fire Rescue rushed to the scene, but nothing could be done to save the two men on board who witnesses pulled from the burning chopper.

Barraga said he and other tried to pull the men out of the wreckage.

The gruesome scene was too much for some to handle.

“I ran back in the gym and started throwing up,” Valerie Senior said. “I couldn’t look at that. It was devastating.”

National Transportation Safety Board investigators said the single-engine aircraft was on a maintenance test flight at the time of the crash.

“Meaning that maintenance was done on the aircraft that requires a test flight after it’s completed,” Air Safety Investigator Patrick Murray said.  “The initial report I got was that there were birds in the area and there was a problem with the tail rotor.”

That tail rotor landed more than a hundred feet away from the rest of the helicopter.

Murray said investigators will analyze witness statements as part of the investigation. Some said they heard an explosion while other said they claimed to see the chopper strike a bird.

The NTSB preliminary report is expected within 10 to 15 days, but a full write-up could take six to nine months, Murray said.

Investigators will remain on scene throughout the day Thursday, a day when the parking lot is usually filled with people going to the nearby church or gym.

Valerie Senior said the experience has taught her a lesson she won’t soon forget.

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“Life is too short. I pray for their families, because that is truly devastating,” she said. “I can’t believe that just happened in front of my eyes.”