Sumerall was hauling wood and other items, including a door that flew forward and slammed into Geissinger's car, said Maryland State Police Trooper K. George.
Trooper R. Miller investigated the accident.
Geissinger was taken by helicopter to Washington County Hospital where he was listed in serious condition Saturday evening.
Sumerall was taken by ambulance to the hospital and also was listed in serious condition.
A passenger in Sumerall's truck, Martin Anthony Neady, 45, also was taken to the hospital. Although his condition could not be confirmed, a hospital spokeswoman said he was not listed in the intensive care unit.
A third car, a 1995 Oldsmobile Achieva, crashed into the back of Sumerall's truck. Neither the driver car - Kristine Joy Burkholder, 15, of Hagerstown - nor passenger - Charlotte Ruth Burkholder, 43 - was injured, police said.
Both lanes of traffic were tied up after the accident, George said.
The collision happened east of Earthcare Road.
Rescue workers from the Wiliiamsport Volunteer Fire Department responded to the scene.