Around 2:30 p.m., authorities received 9-1-1 calls about a crash between a van and the dump truck, according to Los Angeles County fire officials.
Fire officials found the vehicles engulfed in flames and the aviation company employees using commercial fire extinguishers and an emergency crash truck used at the airport to try to put out the flames.
"They're amazing for what they did," said Deanna Howard, whose family owns Howard Aviation Inc. in La Verne near the rear of the Pomona Fairplex.
The employees heard the loud crash and ran out to find the flames starting to take over the mangled wreckage.
"The guys ran back into our hangar and grabbed our fire extinguishers to try to put out the fire," Howard said, adding the flames were shooting about a dozen feet into the air.
"They were so close to the flames and the fire that three of them had to be taken to the emergency room for breathing in smoke and (radiant) burns," Howard said.
One of Howard's employees, Charles Long, got into the truck and drove it to the crash site to try to put out the flames that were burning the driver.
When firefighters arrived, they were able to pull the unidentified dump truck driver from the vehicle.
He was transported to an emergency room with first-degree burns.
The driver of the van was pronounced dead at the scene, fire officials said.
Seven people, including the burned driver, were taken to the hospital. Most sustained minor injuries, officials said.
It wasn't immediately clear how the crash took place.
"These guys have families and they didn't think twice about running out there to help out a total stranger," Howard said. "I think they're amazing."