Seatbelts were not used in either vehicle and would have lessened the injuries if they had been, troopers pointed out.
Members of the Locust Valley Bible Church were playing volleyball at their annual Memorial Day picnic when they heard the crash.
Jason Norris, 24, said he was walking back to serve when he saw the crash.
"I was getting ready to serve and I just happened to look up a fraction of a second before the impact," he said. "I just started running up. I didn't even have shoes on."
Norris, of Middletown, Md., said he immediately ran up the hill from Pleasant Valley Community Park while others called 911.
Norris, who graduated Saturday with a physical education degree from Shepherd College, said an extensive first aid course came in handy. He said he quickly surveyed both vehicles and called 911 to give specific directions and an injury report.
"I've never even called 911 for an emergency, but I did today," he said.
Trooper 1st Class Douglas Bittinger said the pickup truck was heading north on Md. 67, also called Rohrersville Road, and collided with the southbound Jeep. Investigators took dozens of pictures on the ground and a state police helicopter took some from the air in an attempt to piece together the events.
"Obviously, one of them crossed the center line," he said. "But we're still doing our investigation."
Bittinger said a husband and wife in the pickup were injured. He said paramedics found tickets to the Great Boonsboro Carnival.
The teenagers were in the Jeep, Bittinger said. The younger boy was thrown from the Jeep and was lying on his side when witnesses arrived.
After crashing, the Jeep came to rest in the right lane while the pickup truck spun in the air and slid down the hill to the left of the roadway, Norris said.
"He was airborne for awhile," he said. "From my perspective, he just disappeared over the hill."
Two Maryland State Police helicopters landed on the road and flew passengers to the hospital.
Norris said the driver of the Jeep was in the back seat with his feet in the front, he said.
The woman in the truck was lying across the front seat while the man was in the rear cab, Norris said.
Norris said he spoke with the victims who were conscious until paramedics arrived.
Meanwhile, other members of the church picnic ran looking for a fire extinguisher.
"We were beating feet up here. We thought they were going to explode. They were smoking," said Gary Hooper. "It was just a terrible crash. It's sad."
The road was laced with debris from the accident and poignant reminders of the lives involved. A basketball, which Hooper said came from the Jeep, sat to the side of the road.
The frame surrounding the Jeep's license plate read: "My parents worst nightmare."