DALLAS (AP) — Six people were killed after two historic military planes collided and crashed to the ground Saturday afternoon during a Dallas air show, officials said.

“According to our Dallas County Medical Examiner, there are a total of 6 fatalities from yesterday’s Wings over Dallas air show incident,” Dallas County Judge Clay Jenkins tweeted Sunday. He said authorities are continuing to work to identify the victims.

Emergency crews raced to the crash scene at the Dallas Executive Airport, about 10 miles (16 kilometers) from the city’s downtown. News footage from the scene showed crumpled wreckage of the planes in a grassy area inside the airport perimeter. Dallas Fire-Rescue told The Dallas Morning News that there were no reported injuries among people on the ground.

Anthony Montoya saw the two planes collide.

“I just stood there. I was in complete shock and disbelief,” said Montoya, 27, who attended the air show with a friend. “Everybody around was gasping. Everybody was bursting into tears. Everybody was in shock.”

Officials did not specify how many people were inside each plane, but Hank Coates, president of the company that put on the airshow, said one of the planes, a B-17 Flying Fortress bomber, typically has a crew of four to five people. The other, a P-63 Kingcobra fighter plane, has a single pilot.

No paying customers were on the aircraft, said Coates, of Commemorative Air Force, which also owned the planes. Their aircraft are flown by highly trained volunteers, often retired pilots, he said.

Dallas Mayor Eric Johnson said the National Transportation Safety Board had taken control of the crash scene, with local police and fire providing support.

“The videos are heartbreaking,” Johnson said on Twitter.

The planes collided and crashed around 1:20 pm., the Federal Aviation Administration said in a statement. The collision occurred during the Commemorative Air Force Wings Over Dallas show.

Victoria Yeager, the widow of famed Air Force test pilot Chuck Yeager and herself a pilot, was also at the show. She didn’t see the collision, but did see the burning wreckage.

“It was pulverized,” said Yeager, 64, who lives in Fort Worth.

“We were just hoping they had all gotten out, but we knew they didn’t,” she said of those on board.

The B-17, a cornerstone of US air power during World War II, is an immense four-engine bomber used in daylight raids against Germany. The Kingcobra, a US fighter plane, was used mostly by Soviet forces during the war. Most B-17s were scrapped at the end of World War II and only a handful remain today, largely featured at museums and air shows, according to Boeing.

Several videos posted on social media showed the fighter plane appearing to fly into the bomber, causing them to quickly crash to the ground and setting off a large ball of fire and smoke.

“It was really horrific to see,” Aubrey Anne Young, 37, of Leander. Texas, who saw the crash. Her children were inside the hangar with their father when it occurred. “I’m still trying to make sense of it.”