(CNN) -- The fiery crash that Jenelle Embrey witnessed last year prompted her to become a leading critic of the Jeep Cherokee's safety record.
The car driving behind her was rear-ended by a truck on a highway near Winchester, Virginia, in October.
The 1998 Jeep Cherokee crumpled like an accordion when a tractor-trailer hit it at more than 60 mph.
All three occupants were alive after the impact, Embrey says. But two of them died in the subsequent fire.
"The whole thing had gone up in flames," she said. "And we watched those people burn to death."
Desperate to help, her father, Harry Hamilton, ran to the Jeep and broke the windows with his bare hands.
He pulled Zackary Santor out alive. But Heather Santor, his mother, could not be saved. Nor could the other young passenger, Acoye Breckenridge.
"He was hollering and screaming and waving his hands," Hamilton recalled. "And his head -- the back of his head was burning."
Hamilton says the wreck was a searing experience.
"It was days before I could sleep over 10 minutes of time," he said.
But were these tragic fatalities in any way related to the Jeep's design? Or were they simply the unfortunate outcome of an unsurvivable crash?
Chrysler Group, which owns Jeep, says that the model of the Grand Cherokee meets safety standards.
Embrey says the people would not have died if the fuel tank of the Jeep Cherokee was not so far back toward the rear of the vehicle.
"They can take another vehicle and run into the back of that vehicle up to 70 miles an hour, and it doesn't catch fire," she said, "because there isn't a gas tank right there."
But Chrysler Group sees it differently. The company says statistics show that Jeep models such as the Cherokee are no worse or better in rear-end crashes than similar vehicles by other makers from that period.
"The 1998 Jeep Grand Cherokee meets and exceeds all applicable federal safety standards," the company says in a statement, "including the stringent requirements of the applicable FMVSS 301 -- the standard by which a vehicle's fuel system design is evaluated in the U.S. -- and has an excellent safety record over many registered vehicle years."
Embrey has mounted a personal campaign against the Jeep design. Her online petition has drawn more than 100,000 signatures, and she has spent thousands of dollars of her own money to buy billboards criticizing the company.
But Chrysler maintains that the root cause of the Winchester fatalities was the crash impact.
"This tragedy was the result of a violent, high energy crash caused by a distracted tractor-trailer truck driver who rammed into the back of the 1998 Jeep Grand Cherokee at highway speed," it says.
In a rare rebuff, Chrysler Group has refused a National Highway Traffic Safety Administration request for a recall of 2.7 million SUVs.
The government agency says the gas tank design used in 1993 to 2004 Jeep Grand Cherokees and 2002 to 2007 Jeep Libertys is unsafe. Chrysler says that the design of the gas tank is commonly accepted in many other vehicles.
It's the first time since 1996 that an automaker has fully challenged a recall demand from the safety agency.
CNN's David Gracey contributed to this report.