SEMINOLE — Christina E. Tournant's family joked when she was growing up that she was wise beyond her years, a precocious kid who could figure out almost anything.

"We always said she was an old soul," said Christina's mother, Tava Wilson. "She just understood things."

With that burning intelligence, Christina became valedictorian of Osceola Fundamental High School and enrolled at the Massachusetts Institute of Technology. In recent weeks, she came home from MIT to recover as she fought a nervous system disorder causing pain and circulatory problems.

On Thursday night, Christina stood high on a parking garage at Tampa International Airport. At 8:17 p.m., she sent a text message: "I love you, mom."

At 8:25 p.m. Christina, 17, was found dead after she apparently jumped from the garage. On the back of a photo of herself and her mother that Christina left behind, the teenager wrote a note expressing regret at the one puzzle she would not solve — her health.

"Sorry," she told her mom, "I couldn't keep fighting."

The death of the popular 2014 Osceola Fundamental High graduate, an MIT student majoring in biomedical engineering, has shocked two communities. At MIT, where Christina was a freshman, students gathered in vigil at her dorm Saturday night. At Christina's home in Seminole, her mother made funeral arrangements for the pretty teenager with a bright smile whose family said hated letting the world see that she was so sick.

"It was physical pain that definitely led to emotional pain," Wilson said at her home, fighting to keep her composure. "She was very stoic and didn't want to let on how horrible she was feeling . . . She was really stoic to a fault."

A spokeswoman for the Tampa airport reported a suicide by a person who jumped from a parking garage Thursday. The death is being investigated.

In Seminole, teachers, friends and family remembered a vigorous student and a talented athlete on the swim team.

Joshua Engelhardt, who was Christina's advanced placement history teacher when she was a junior at Osceola Fundamental, said she was one of the best students he ever had. "She was incredible," he said.

"If there was anything she didn't understand, then she asked more questions than anybody else in class," Engelhardt said. "She was very driven. She had a motor that I never did see stopping."

Christina's is the eighth MIT death in the past year, including at least five suicides. MIT president L. Rafael Reif emailed a letter to the entire student body of the Cambridge, Mass., university Friday offering counseling and other assistance to students or faculty upset at the death.

"I know this news will have a profound effect on every one of us," Reif said. "This is a moment when we need each other, a moment for caring, understanding and kindness. We will come through this tragic period together."

Christina's death does not provide the stereotypical narrative of a student overwhelmed by the academic rigors of a prestigious university. Her mother said Christina was earning As at MIT.

"Even though she wasn't feeling good and everyone knew it, she did persevere," Wilson said.

Wilson said her daughter suffered from postural orthostatic tachycardia syndrome, or POTS, a disorder of the autonomic nervous system. The illness, which often afflicts young women, causes a range of debilitating symptoms, from an increased heart rate to circulation problems and, in Christina's case, severe pain and digestive problems. The syndrome, whose cause is not well understood, can leave sufferers completely disabled.

Poor circulation made Christina cold in the pool, her mother said, so she switched from swimming competition to diving and, though she was a diver for just three months, she was named a "rookie of the month" in February in the Eastern College Athletic Conference after she earned a spot at the NCAA Diving Regional Competition.

Wilson said her daughter suffered from POTS for two years, but she became acutely ill in December. The mother went to MIT on Feb. 16 and stayed with her daughter nine days, then brought Christina home. MIT confirmed Christina was on medical leave.

On Thursday, mother and daughter had plans to visit a doctor and maybe get a pedicure. Christina was getting frustrated with all the attention and that so many people were asking her how she was doing, Wilson said.

Christina told her mom she would spend Thursday night at her father's house. Her parents are divorced. But instead of driving to her dad's home in Seminole, the teen made her way to the airport in Tampa.

Christina left behind photos of herself with family and friends. On the back of each, she scribbled a note.

And then, she sent that final text message to her mom from the parking garage.

"She was that kid that was just happy," Wilson said, noting that her daughter was always up for any adventure, any challenge. "She wanted to do all kinds of fun things."

Christina's funeral arrangements are incomplete. Besides her parents, she leaves behind a brother, age 20, and a half brother, 18 months.

Times researcher John Martin contributed to this report. Contact William R. Levesque at levesque@tampabay.com or (813) 226-3432.