Jamie Grimsley, 18, who graduated from Hayfield Secondary School in Fairfax County and was about to begin her freshman year in college, was killed early yesterday morning when she crashed the SUV she was driving into a tree. Three of her passengers were injured.

"It still doesn't feel real," said Allie Cocker, 17, a Hayfield senior who came to the crash site off Route 123 in Fairfax and placed a photograph, of herself and Grimsley at a cheerleading tournament, beside the tree. "We were getting ready for her to leave anyway, but definitely not like this. Summer of 2005 is never going to be the same, but we still had fun with her while she was still here."

About 1:50 a.m., Grimsley was driving with three friends, heading west on Lee Chapel Road -- a winding, two-lane road -- when she veered to the right, swerved back onto the asphalt and then lost control, Fairfax police said.

The Infiniti SUV crossed the opposite lane, slammed into a tree and flipped, police said.

Grimsley died at the scene. The three passengers -- two males and one female -- were taken to Inova Fairfax Hospital with injuries that were not life-threatening, police said.

Officer Shelley Broderick, a Fairfax police spokeswoman, said she did not know whether anyone was wearing a seat belt or whether alcohol or speed was a factor in the crash.

Police said that they have not determined the cause of the crash but that the investigation was continuing.

"Our accident reconstruction guys are still working on it right now," Broderick said. "It's tragic when anyone dies in a fatal accident, but this is an 18-year-old girl. It's unfortunate."

Friends who came to the scene said that Grimsley and her friends were returning from a party and that her boyfriend was in the vehicle.

A man standing outside Grimsley's home in Mason Neck told a reporter that Grimsley's family declined to comment.

Everyone called Grimsley "Allie" -- short for her middle name, Alexandra, friends said.

As the captain of her cheerleading team during her senior year, Grimsley was well-known for her outgoing style and her desire to know virtually everybody.

She had a huge laugh that could be heard for a long way, she loved joking around and when she wasn't tossing others up in the air during a cheerleading routine, she could be seen wakeboarding on the Potomac River, friends said.

Grimsley had worked at a clothing store in Fair Oaks Mall and had pumped gas for boats at Belmont Bay, they said.

"Outgoing. Crazy. Would talk to anybody. Life of the party," said Megan Arline, 18, who went to the crash site.

Grimsley's cheerleading coach, Ashley Lintott, said the 18-year-old was to leave soon to begin classes at West Virginia University. Grimsley thought about pursuing a career in criminal justice, Lintott said.

"She told me she was thinking about becoming a CIA agent or working for the FBI," Lintott said. "She was kind of goofy. One time, she got the kids to put shaving cream on my house. They put on ski caps and black turtlenecks. She was like my little sister."

At the crash site, Cocker and another cheerleading teammate, Andrea Pasquel, 17, wrapped an orange ribbon around the tree.

As Cocker placed the ribbon on the tree, Pasquel stared at the bark, fingering the chips of car paint.

Jamie Grimsley, 18, who was cheerleading captain at Hayfield Secondary School, was to attend college in the fall. She was the "life of the party" and "would talk to anybody," a friend said.