Early morning motorists on Interstate 95 near Oxon Hill were terrorized yesterday by three teenage youths who stood in traffic and began hurling rocks at oncoming cars, injuring seven people, one critically, and damaging about 25 vehicles.

The incident occurred about 2:30 a.m. on I-95 near Livingston Road. Maryland State Police said that witnesses reported the three teenagers were standing in the Beltway's traffic lanes as they threw dozens of rocks at approaching cars.

The rocks, which weighed 5 to 15 pounds, crashed into windshields, slammed into fenders and caused some motorists to lose control of their vehicles momentarily, police said.

A passenger in one of the cars, Destiny Morris, 15, of Hagerstown, Md., was struck in the head by a rock and was listed in critical condition yesterday at Southern Maryland Medical Center in Clinton. Fliers distributed by police yesterday at apartment complexes along Livingston Road asked for help in solving the case and mentioned the girl's fight for survival.

"This little girl's not even 16 years old yet," said her father, Ellis Morris, from the hospital waiting room. "She doesn't even know what life is all about, and the doctors are telling me she might not make it because somebody threw a rock. . . . It just doesn't make sense."

One witness said the rock throwers apparently used some trickery to get a better shot at their targets. Robert Brannigan, 27, of Baltimore, was on the last leg home from a Florida vacation when he approached the Indian Head Highway exit near Livingston Road and saw a body lying in the road.

"At first, I couldn't see him because it was so dark," Brannigan said. "I thought someone was hurt. . . . When he started to get up, he had a boulder over his face and he started running toward the car. I swerved. It was the wildest thing." The rock crashed through Brannigan's rear window, but no one was injured.

Brannigan said state police told him that "something like this has been going on for a couple of months." Police, while acknowledging that rock-throwing incidents on the Beltway are not uncommon, said they had never seen an incident of such magnitude.

"It was a real mess," said Sgt. Vernon Herron. "Those cars were moving at 55 mph, and when a big rock hits you at that speed, it's a very, very serious incident. It's not fun and games."

Besides Morris, only one of the injured, Kelly Moody, of Manassas, was still hospitalized yesterday afternoon. Moody was in good condition at Prince William General Hospital with a chin and chest wound caused by a rock that flew through the windshield. Her friend, Gloria Scott, who was driving, said the two were returning from a nightclub when she heard a loud "pow," thought she had blown a tire and pulled over.

"And then I saw that Kelly had been hurt," she said yesterday from Moody's hospital room. "I could not believe it. I did not see a soul. There was nobody else on the Beltway right then except us and a truck."

Rodney Marbury, 27, of Landover, told his mother, Delores, that he was traveling the same stretch of road about the same time when he slowed down because of a commotion up ahead. Suddenly, he said, someone ran up to his car and threw a large rock inside, breaking Marbury's arm. Marbury, like several of the others who were injured, spent most of yesterday sleeping.

"He said he was dazed by the whole thing," Delores Marbury said. "But it scared me to death."

For the Morris family, crossing the rock throwers' path gave a terrible ending to what had been a pleasant visit with friends for Destiny Morris.

"We're talking about sick minds," Ellis Morris said about the rock throwers. "People need to get involved if they know something and stop them. They're crazy."

Witnesses told police that three young males, between the ages of 14 and 18, were seen running from the scene. Anyone with information about the case should call the Maryland State Police, Forestville Barracks, at 568-8101.