Lviv, Ukraine ? A fighter jet clipped the ground and sheared through a crowd of spectators Saturday at an air show in western Ukraine before exploding in a ball of fire, killing at least 78 people and injuring 138 in the deadliest air show accident in memory.

The SU-27 aircraft slid backward on its wingtip and nose through hundreds of spectators, then cartwheeled, throwing off flaming debris, until it exploded at the Sknyliv air base in the city of Lviv.

Firefighters extinguish flames from the wreckage of an SU-27 jet that crashed into a huge crowd of spectators at an air show in Lviv, Ukraine. The two crewmen ejected and survived, but at least 78 spectators were killed and dozens of others were injured in the accident Saturday.

Bohdan Hupalo, 18, said he was posing for a picture when the plane came down. He dove to the ground and saw the jet race over him, missing by only a few yards.

“There weren’t any survivors among those who fell down late they were cut down like grass,” he said. When Hupalo opened his eyes, he said he was surrounded by human remains.

“I will never forget this tragedy,” he said from his hospital bed, where he was being treated for an injured back.

After the crash, parents frantically searched for missing children and used the public address system to call out their names. One group of children with cuts on their faces and arms sat stunned on the ground.

The Emergency Situations Ministry said 138 people had been treated at hospitals in Lviv, and 24 who were lightly injured had been released. It said the death toll could still rise because many of the injured were in critical condition,

The two crew ejected and survived, the Defense Ministry said. They suffered back injuries, medical officials told Interfax news agency, but they were seen walking away from the crash scene without assistance.

The plane was in the sky for about two minutes and had been performing advanced maneuvers. Then it went silent and headed toward the ground, banking left, with its wingtip shearing trees and touching another plane on the ground. It then hit the tarmac.

The Defense Ministry’s western operational command said engine failure was the preliminary reason for the crash, but ministry headquarters in the capital Kiev declined to comment on the cause and refused to confirm an engine malfunction.

President Leonid Kuchma, who cut short his vacation in Crimea to rush to the accident scene, implied that a technical fault could have been to blame.

“This equipment has already functioned to its technological capacity,” he said after his arrival in Lviv. Much of the country’s air force arsenal is leftover from the Soviet era and in poor condition.

“We don’t know anything absolutely except that the pilots were the most experienced, of the highest class,” Kuchma said in comments shown on state television.

After Saturday’s crash, Kuchma fired the commander of the air force and the top officer from the 14th Air Corps, to which the jet belonged.

Government investigators began questioning the jet’s crew, along with other witnesses, and watching video of the crash. Prosecutors also started an investigation.

One of the world’s most deadly previous air show crashes was at a U.S. air base in Germany in 1988, when Italian jets performing a complicated maneuver collided and spiraled into the crowd, killing 70 and injuring at least 400.