Family members and friends have been left heartbroken and baffled after an 18-year-old high school senior died suddenly on Tuesday, just hours after feeling ill. Madison Small, from Ashburn, Virginia, left school early on Monday and, after she woke up in the night with a severe headache, she was rushed to hospital. By Tuesday afternoon, her father, Tim Small, had contacted the Broad Run High School to let staff know that his youngest daughter had passed away that morning. The Virginia Medical Examiner's office is now investigating her death and an autopsy has been ordered, but no cause has yet been given. Loss: Madison Small, pictured, passed away suddenly on Tuesday morning after feeling ill on Monday; the Virginia Medical Examiner is looking into the cause of her death but so far a diagnosis has not been given . Mr Small told WUSA9 that the family has also not received a diagnosis for his daughter's illness. He said she had seemed the picture of health over the weekend, when they played catch together. The medical examiner said it would likely take at least a week to determine what had killed her. Her close friend Devan Rook told the Washington Post that she had thought nothing of it when her friend went to the school nurse on Monday afternoon. 'Didn't think anything was wrong with her,' she said. 'In the middle of the night, she woke up complaining of headaches and stuff, and they took her to [Inova] Loudoun Hospital and realized it was pretty serious. 'They couldn't handle it there, so they medevac-ed her over to [Inova Fairfax Hospital]. At that point, she wasn't doing too well, and several of her organs were shutting down.' Public Health and school district officials said they do not have reason to believe her illness poses a risk to other students, particularly because last week was spring break, WUSA9 reported. Loved: Madison's family said she was otherwise healthy when her health suddenly declined on Monday . Family: Her father Tim Small, pictured center, spoke at a candle-lit vigil held for the teenager on Tuesday evening. Madison is pictured left with her older siblings and parents . On Tuesday night, just hours after news of their her death, hundreds of friends, classmates and family gathered for a candle-lit vigil at the school. Friends remembered Small as a talented softball player who had happily mentored younger members of the team. She was also excited about starting Virginia Tech in the fall, they said. School Principal Dave Spage, who broke the news to parents in an email on Tuesday, said he thought there were as many as 400 or 500 people at the vigil, which he said 'speaks to her circle and her involvement here', NBC reported. Madison's father, who also has an older daughter and son with his wife, spoke to those who had gathered. 'Life can be short, we found that out today,' he said. 'Make the most of it: love each other. Don't get bogged down in the little nitpicky crap. Put that aside. Life's too short.' Remembered: Hundreds of people gathered for a candle-lit vigil following Madison's death on Tuesday . Support: Her varsity softball teammates wear their jerseys and line 2nd base as a tribute to Madison . Vigil: Friends lit candles as they shared memories of the beloved 18-year-old on Tuesday . Memorial: Classmates places flowers on Madison's desk after she was taken fatally ill . In a Facebook post shared widely between Madison's friends online, she wrote a touching post in 2011, quoting Winnie The Pooh. 'If there's a tomorrow when we're not together, there's something you must always remember,' she wrote, beneath a smiling photo of herself. 'You're braver than you believe, stronger than you seem, and smarter than you think. But the most important thing is even if we're apart, I'll always be with you.' Counselors will be at the school to help students, Spage said.
Madison Small woke up feeling ill on Monday night so was rushed to hospital, but her organs began shutting down and she died on Tuesday .
Her parents have not been given a diagnosis for their daughter's illness and the medical examiner's office is now determining the cause .
Hundreds of students and family members gathered for a candle-lit vigil on Tuesday night, where she was remembered as a great athlete and friend .