The charred cab of a tractor-trailer was sitting atop the black and twisted wreckage of what Franklin County Coroner Jeffrey R. Conner said appeared to be the Toyota pickup truck.
The crash happened shortly after 2 p.m.
"I saw the tractor-trailer go right through the truck," said Joseph Morning of Weldon, N.C.
The accident involved a 1991 Mack Truck hauling a load of Holsum bread, a 2004 Toyota Tundra driven by Bonner and a 2004 Freightliner pulling a double trailer, state police said.
The Freightliner driven by Michael Stehley, 41, of Newport, Pa., stopped in the right lane of southbound I-81 due to a traffic backlog and the Toyota pickup driven by Bonner stopped behind the Freightliner, police said.
The Mack Truck driven by Enoch Neidig, 51, of Elysburg, Pa., struck Bonner's pickup, which in turn struck the Freightliner, police said.
The bread truck, with the pickup smashed beneath it, went off the west side of the highway, through a fence and into a farm field.
The bread truck, the pickup and the rear trailer of the Freightliner truck burst into flames. Firefighters from several companies were still hosing down the wreckage more than an hour after the crash.
The trailer of the bread truck burst open in the accident, spilling loaves and plastic trays into the field. The rear trailer of the Freightliner was hauling artificial food flavoring and the scent of cherries was in the air.
The other trailer was filled with batteries, said Franklin County Hazmat coordinator Gary Himes. The trailer was damaged, but the cargo was not leaking, he said.
"That'll have to be shored up and off-loaded," Himes said.
Southbound I-81 was closed from Exit 10 near Marion north to Exit 14 in Chambersburg, Pa. The northbound lanes also were closed after the accident because of the smoke spreading across the highway and to allow emergency vehicles access to the scene.
At about 4:30 p.m., a state police helicopter landed in the northbound lanes. Deputy Coroner Kenneth L. Peiffer said he was going up in the helicopter to get aerial photographs of the scene, which stretched for about 100 yards along the highway.
Morning said he and the driver of the Freightliner truck helped pull the driver of the bread truck from the wreckage. Morning said he saw cuts on the man's arms and face, but he did not appear to be seriously injured.
Pennsylvania State Police said the man was taken to Chambersburg Hospital.
"When we got him out, he was just standing there in front of the truck" as it burned, Morning said. "We told him he had to move."
Conner said another incident farther south on I-81 may have played a role in the accident. He said there was a road crew south of Marion and the left lane already was shut down. With traffic already slowed, he said a medical emergency in the work zone was reported and traffic was brought to a halt.
Emergency personnel at the scene expected the southbound lanes to be closed for several hours to allow for the investigation and cleanup.
"There was an awful lot of black smoke," said Don Hagerich of Carlisle, Pa., who works for the Pennsylvania Department of Environmental Protection office in Chambersburg. He was in Greencastle, Pa., when he got the call to go to the scene.
Hagerich said he could see the smoke more than five miles away and arrived as the first firetrucks reached the scene. Several other department personnel were there to gauge the possible environmental impact of the accident, primarily from diesel fuel, Hagerich said.
Southbound traffic was backed up for several miles. A few hundred yards north of the accident, fire police helped maneuver vehicles to an emergency crossing in the median so they could turn around and go north.
The crash turned the interstate into a parking lot of tractor-trailers and passenger vehicles and tangled traffic on U.S. 11, Pa. 316 and other secondary roads as vehicles were detoured and motorists tried to find ways around the gridlock of local roads.
The Franklin County 911 Center issued a news release at 7:33 p.m. Thursday night, saying that one lane of northbound I-81 was open and that the southbound lanes would remain closed for several more hours.
Traffic was rerouted as far east as Waynesboro on Thursday night.