The Buick ricocheted away from the three men, who were standing between Laing's cruiser and a gold Dodge Daytona.
When he saw the southbound Buick go into the median and roll several times, Laing jumped over the guardrail with Fred Elliot, 33, and his stepson Jason Whittington, 20, both of Kearneysville, W.Va.
The Buick came to rest about 120 feet away from them.
Buick driver Shari Hood, 46, and a passenger believed to be her husband, James Hood, 46, both of Martinsburg, were taken by ambulance to City Hospital and then flown to Inova Fairfax (Va.) Hospital. Both were in critical condition on Friday, a hospital spokeswoman said.
A couple from Wingdale, N.Y., in the Winnebago were taken to City Hospital. Tom Fuhr, 62, had a severely cut lip and Carol Fuhr, 60, had small cuts on her face, Laing said. Both were treated and released, a hospital spokeswoman said.
The Fuhr family dog was taken to Inwood Veterinary Hospital for observation. The family cat wasn't found, but may have been hiding somewhere in the Winnebago, Laing said.
Elliot and Whittington were not hurt. However, each were charged with misdemeanor possession of marijuana in connection with the traffic stop, Laing said.
All four lanes of Interstate 81 were shut down for an hour at the 12-mile marker, near an exit for the Martinsburg Mall. The northbound lanes were closed for another hour, Laing said.
Laing said his presence may have lessened the severity of the accident.
Northbound traffic was probably going about 20 mph slower than normal because of the cruiser, giving the Winnebago more time to react, he said.
This was the second time Laing witnessed an accident. The last time was on U.S. 11 in Berkeley County, W.Va., a year or two ago.