ATLANTA (AP) — A small passenger airplane dropped from the sky and grazed the hood of a tractor-trailer before it crashed into an Atlanta interstate Friday, killing all four people aboard and starting an intense fire on the busy road.

The Piper PA-32 took off from DeKalb Peachtree Airport and apparently ran into trouble not long afterward, Federal Aviation Administration spokesman Kathleen Bergen said.

Motorist Don McGhee, 48, said he saw the aircraft nearly hit a traffic light pole near the highway onramp.

"It looked like it was struggling. You could see him trying to get the nose of the plane up. It was edging up, and then it just dropped," McGhee said. "It was just a huge fire, just smoke and fire."

Witnesses said the blaze prevented anyone on the ground from helping any victims in the wreckage. Those who tried included commercial truck driver Gerald Smith.

Smith said that as the aircraft plummeted, he had just enough time to slam on his brakes. He saw the plane swooping in low toward the passenger door of his tractor-trailer.

"It grazed my hood, and the next thing I knew I looked over to my left and that plane had crashed against the median wall," Smith said. "I first started to walk over there, but it was blazing up and there was no way to help anybody try to get out of the plane. I just turned and dropped my head and walked away."

DeKalb Fire Capt. Eric Jackson said all four people onboard died in the crash, though authorities did not immediately release the names of the victims. The plane nearly struck a vehicle driven by a former DeKalb County firefighter and a truck.

"It's a miracle, literally a miracle, that no other cars were hit," Jackson told reporters.

The tail, other wreckage and charred concrete could be seen at the median barrier where the plane crashed. Smaller debris littered the area, including a propeller lying on the roadway about 40 feet from most of the wreckage.

Emergency officials shut down Interstate 285 in both directions, causing large traffic jams. The Georgia Department of Transportation said some lanes near the crash site could be closed for eight hours.

Jackson said the scene of the crash needed to be preserved so investigators can determine what happened.

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Associated Press reporter Ray Henry contributed to this report.