Ross Sweeney saw his friend Tony Brensinger's four-wheeler flip over a jump and spin into the air Tuesday night, dropping Brensinger onto a dirt lane and leaving him unable to breathe.

"Don't do this to me," Sweeney told Brensinger, who was lying on his back, bleeding from his mouth and shaking as he tried to get air. Sweeney ran onto Route 234 to stop a car to call for help, and an hour later, his best friend was airlifted to Prince George's Hospital Center.

Two days before, a 15-year-old died in Calvert County after his ATV crashed into a pine tree.

And this year on the same St. Mary's County farm, a young girl was airlifted from the scene of the collision of two four-wheelers, said Charles "Banjo" Nelson, who came out of his house in his slippers to see what had happened Tuesday evening.

It's a growing problem, said Mike Huseman, chief of the 7th District Fire Department, one of the volunteer units that arrived at the scene near Clements. "This past year we've had at least three or four [ATV accidents] just in our area, and other communities have the same problem. . . . All the kids ride them in today's world."

For farmers and landowners in the area, it's a worry. Nelson has allowed riders to use the land he farms, but he gets scared when he sees them jumping and racing around.

"I'm going to post the farm," he said, "stop them from riding now." He watched the emergency workers strap Brensinger onto a stretcher, his face lighted by the whirling ambulance lights.

"You can't stop them," said Ken Nelson, who grows grain near his brother's farm. He said his son smashed into a tree on one when he was 13. "Soon as he got it fixed up, he started driving again."

And some farmers have found that running riders off their land can cause trouble. "You get some enemies against you if you try to stop them," Nelson said. "Maybe they do something to your barn. It has happened."

Sweeney and Brensinger, who are both 18, hang out together all the time, four-wheeling or playing PlayStation, fishing or hunting. They graduated from Leonardtown High School last spring, Sweeney said.

Brensinger had just fixed up his yellow Honda four-wheeler Monday, Sweeney said, so the two were trying it out Tuesday to see how it ran with more power. "He was rolling," Sweeney said, really fast before he took the jump. "Maybe 20 or 30 miles per hour."

Sweeney said he didn't know what to do, seeing his friend lying there, one work boot on, the other where it landed by some corncobs in the field. "I tried not to cry," he said. "I didn't want to get him upset."

Cars had lined the road, ambulances came, and Brensinger's stepfather knelt by him, rubbing his head and talking to him. A white light appeared just above the horizon in the dark: The U.S. Park Police helicopter was coming. Soon leaves were flying as it landed on a neighbor's yard. Sweeney got back on his red four-wheeler and put his mud-spattered helmet back on, watching them lift his friend into the helicopter.

"I'm getting rid of these," he said, looking at their four-wheelers. "I just don't want to deal with it anymore."

The helicopter lifted off, over the cars backed up on the highway. Sweeney started his motor and rode home, dirt flying under the wheels.