MANCHESTER, Pa.—State police say a man found dead on a central Pennsylvania highway had hitched a ride on the back of a tractor-trailer not long before he was apparently struck by at least one vehicle.

Investigators say surveillance footage shows 24-year-old Michael Ruppert on the back of a tractor-trailer as it left a convenience store early on the morning of Oct. 27. Ruppert's body was found a couple hours later about 10 miles away on Interstate 83.

Trooper Adam Reed says Ruppert tried to get into the truck but was refused by the driver. The video from the store shows Ruppert hanging off the back of the trailer as it pulls away.

Reed says investigators are still trying to determine how Ruppert's body ended up on the highway.