In high school, the teens were dancers. Ruehl recalled them as "sweet, wonderful girls who were very pleasant, and always said 'hi' to me in the hallway."

Ruehl said Tuesday was a "very difficult day" at Mount Hebron for the staff, who are preparing to welcome students back to school next week.

"There were a lot of tears" as well at Patapsco Middle School, where Nass attended, said Cynthia Dillon, its principal.

"When you go into education, you never expect to outlive your students, and for Elizabeth to be as accomplished as people told me she was, it's exceptionally hard," Dillon said.

On Tuesday afternoon, the Mayr family's driveway was filled with cars, and others continued to arrive with expressions of sympathy.

"She was a beautiful and caring person who was always there for her friends and family," said Courtney Ross Hannemann, Mayr's first cousin. "She loved caring for children and was looking forward to becoming a nurse. My husband and I were fortunate to have her care for our two young daughters this summer. I am grateful for the memories we had with her. On behalf of our entire family, I can say she will be forever missed."

Outside the Nass residence in Ellicott City early Tuesday afternoon, family members declined to comment.

Mount Hebron senior Tish Carmona, a family friend, stopped by the house to drop off a rose and express her condolences.

"She was always very nice and very pretty, and was someone people would look up to," she said. "So many people are praying for them. We love them."

Howard County Councilwoman Courtney Watson said both families were active and well respected in the community. She said Nass' mother was passionate about education issues, and was involved in the Parent Teacher Association campaign to build a new high school — Marriotts Ridge — in the community. Her father was active in the Howard County Chamber of Commerce, Watson said.

"I think everyone is feeling sorrowful today," Watson said. "We're really tying to come together, and the community as a whole is reaching out to let them know that we are mourning with them."

Nass, who worked as a ski instructor at the Massanutten resort about 12 miles from the James Madison campus, was honored in 2002 when she was 9 years old for her high grades and community service. Along with some friends at Hollifield Station Elementary School, she collected nearly $2,500 for the Red Cross to help victims of the Sept. 11, 2001 terrorist attacks.

"I just thought it was really terrible how people lost their family members and people were in the hospital and didn't have enough money to pay," Nass told The Baltimore Sun at the time.

Nass said at the time that she played the French horn, participated in Girl Scouts and played lacrosse and basketball. She said she liked horseback riding, singing and performing in front of audiences.

For her achievements, she was awarded a $1,000 college scholarship.

Late Tuesday, it still was not clear why Nass and Mayr decided to perch above Main Street in Ellicott City, although it is not unusual to find people hanging out by the tracks, "sometimes teenagers, sometimes homeless people," said Sherry Llewellyn, a police spokeswoman.

But on Aug. 12, Nass tweeted to Mayr to let her know that she wanted to get together one last time before the end of their summer vacations.

Both Twitter accounts were public until Tuesday afternoon. Mayr's @r0se_petal account was made private, while Nass' @liznassty account appeared to have been deleted.

Near the site of the accident, Paige Fuss, owner of Ellicott City Weddings and Events, stood on Main Street creating the beginnings of a makeshift memorial to the victims at the entrance of Tiber Park.

She tied two big pink bows onto the iron fence, and set two cardboard coffee containers on the ground, one with a spray of yellow roses, another with a cluster of pink flowers. Three of her six children went to Mount Hebron High School with the two victims, she said.

Alexis Estomin, a fellow 2010 Hebron graduate who attended the vigil, said the size of the crowd showed how much both women were loved.

"They were beautiful, intelligent, funny girls who were going to do really special things," Estomin said.

Baltimore Sun reporters Erica L. Green, Scott Calvert, Mary Gail Hare and Arthur Hirsch and Baltimore Sun Media Group reporter Lindsey McPherson contributed to this article.