John Travolta's 16-year-old son, Jett, died Friday morning at the family's vacation home in The Bahamas after what the family's lawyer says was a seizure-related incident.
The family, including Jett Travolta's mother, Kelly Preston, and his 8-year-old sister, Ella, had been celebrating the New Year in The Bahamas.
"A nanny attempted to revive him, all attempts were made, but he couldn't be revived," Travolta's attorney, Michael Ossi, who is also in The Bahamas, told ABCNews.com. "They tried as hard as they could to revive Jett."
Ossi added that the teenager "has had seizures in the past, but they were controlled. This one couldn't be."
The seizure may be only part of the story. Royal Bahamas Police Force spokeswoman Loretta Mackey told the Associated Press that Jett Travolta died from hitting his head in a bathtub.
Jett Travolta's health made national news in 2002. It was at this time that his mother disclosed that at age 2 he had had a poorly understood condition known as Kawasaki syndrome, a collection of symptoms that stem from swollen arteries.
Researchers believe that inflammation from Kawasaki syndrome, or KS, can lead to convulsions and seizures.
KS primarily affects children under the age of 5, though it can occur in older children. According to the Centers for Disease Control and Prevention, about nine out of 100,000 children have KS. Incidence is higher among Japanese and Korean children, though KS can occur among any ethnicity.
However, KS expert Dr. Robert Frenck, a professor of pediatrics in the division of infectious disease at the Cincinnati Children's Hospital, said KS is not usually associated with deadly seizures -- especially in children who have already recovered from KS, which he said is a temporary condition.
"If there's a major complication, and if someone dies from it, it is a [coronary] aneurysm," he said. "It doesn't happen frequently, but that is what we really worry about. ... That can set the kids up for a heart attack."
Frenck added that the only type of seizure that can occur in patients with KS is a febrile seizure, which arises from a high fever.
The New York Post and other media outlets have suggested in past reports that the Travolta's son has autism, though the family has always maintained that their son's condition is KS. Autism is also associated with seizures.
"There is a relationship between autism and seizures; as many as 40 percent of children and young adults with autism may experience seizure, and adolescence is a particular time of vulnerability," said Dr. Bryan King, director of child and adolescent psychiatry at Seattle Children's Hospital's Research Center for Health Services and Behavioral Research.
"There are hormonal changes that could increase the risk of seizure, and certainly there are ongoing brain changes that take place during adolescence, but no one knows why the risk increases in older children."
Regardless of the cause, Ossi said that the family is now grieving. He added that the incident "is the worst pain any parent can experience, the loss of child."
Speaking for John Travolta, Ossi said, "This is the worst day of his life."
Ossi said that Dr. Mark Smith, the Travolta family doctor, plans to give a statement after the autopsy.
ABC News' Eileen Murphy, Lauren Cox and Kirk Fernandes contributed to this report.