(CNN) All nine people aboard an aging cargo plane making its final military flight Wednesday were killed when the aircraft nosedived onto a Georgia highway.
The Puerto Rico Air National Guard WC-130 was carrying nine crew members when it crashed, the Guard said in a statement. It was flying from the coastal city of Savannah, Georgia, to Tucson, Arizona, where it was to be decommissioned.
The plane involved in Wednesday's crash was at least 50 years old, according to an official familiar with the aircraft.
"Nine crew members died in the accident, but until their families and relatives are notified, we cannot give their names," Brig. Gen. Isabelo Rivera said. "Our prayers, thoughts and condolences to the families and loved ones of our aviators."
One witness said the plane made a "loud, strange noise" just before the crash. Another said the ground shook as if a bomb went off when it hit.
Video from a business near the crash shows the horrifying final moments of the hulking plane, a version normally outfitted to do weather reconnaissance.
The jet, with four turboprop engines on its overhead wing, banks left as it comes down. The plane then heads straight down behind trees. Seconds later a fireball and thick black smoke appear.
Puerto Rico's governor sent his condolences.
"While we are waiting for more information regarding this unfortunate accident, my thoughts and those of Beatriz are with the families of the crew. They will receive our support and that of the National Guard of Puerto Rico in this process," Gov. Ricardo Rosselló said.
President Donald Trump tweeted his support.
"Please join me in thoughts and prayers for the victims, their families and the great men and women of the National Guard," he said.
All the airmen were from Puerto Rico, officials said.
Truck driver Roger Best works for a transportation company in Garden City, about 4 miles south of the crash, and saw the plane overhead before it plummeted. It was so low when it passed over that it rumbled the ground beneath his rig, he said.
His company handles hazardous materials, he said, expressing gratitude that the aircraft didn't crash in his immediate vicinity.
"If he did this area is a giant bomb and this whole (five-mile) radius would have blown up," he told CNN over Facebook, calling the pilot a hero for avoiding the area. "He barely made it over the tree line (and it) looked as if he tried to turn and nose dive straight into the ground right in front of me."
Christian Freeman saw the WC-130 go down, he said. First, he heard a "loud, strange noise," he said.
"I looked over to my right and seen the plane at very low altitude and making a hard left turn to the ground," he said.
It happened so quickly, he didn't have a chance to pull his phone out until after it exploded, Freeman said.
"It was horrible," said Denver Goodwin, who works at a wrecker service down the street from the crash. "The ground shook like a bomb was going off. All the people in the building started panicking. It was absolutely horrible."
Mary Hennessy Cogar was at her place of employment in Garden City and said she felt the impact.
"Our building shook and the lights flickered. We heard a boom of the crash and then a louder boom of the explosion," she said.
A tweet from the Savannah Professional Firefighters Association showed the tail of the plane protruding from thick smoke and fire.
There were no injuries on the ground.
"As far as we know, no cars were hit, which is an absolute miracle," said Gena Bilbo, spokeswoman for the Effingham County Sheriff's Office.
The crash occurred a few miles away from the Savannah/Hilton Head International Airport, off state Highway 21, airport spokeswoman Candace Carpenter said.
Maj. Paul Dahlen said the plane, from the 156th Airlift Wing in Puerto Rico, had been in Savannah for "a number of days" undergoing routine maintenance before heading to the Aerospace Regeneration and Maintenance Group in Arizona.
"We don't know the cause of the crash," he said.
The WC-130 is a variant of the C-130. Produced continuously since 1954, the C-130 is a reliable and versatile aircraft with several iterations. It can be outfitted for transport, reconnaissance, search and rescue, research, refueling, patrol or as a gunship.
Last month, the chairman of the House Armed Services Committee, Rep. Mac Thornberry, released a statement saying the "readiness of the military is at a crisis point" after reports that 16 American service members had been killed in noncombat aircraft crashes over a matter of weeks.
Last summer, the Marine Corps ground its fleet of KC-130Ts, another variant of the C-130, following a crash that killed 15 Marines and one sailor in Mississippi.