(CBS News) - Dylan Winnick, 12, attended a birthday party last weekend, hung out with his family and went to the pool in his neighborhood, his family said. He was struggling with what the family thought was a cold, but otherwise seemed fine, CBS Miami reports.
According to his 16-year-old brother Sebastian Roa, Dylan developed a fever on Monday. By Tuesday, he was complaining of his bones hurting. Dylan stayed home from school that day and his father, Sergio, told reporters that his son appeared to be feeling better.
Sergio left the house. When he returned home, Dylan was dead.
"My message to all parents: be careful with your kids," he told reporters through an interpreter. "There's a new flu out there and is no vaccine for it. There is nothing."
Sebastian is devastated. He said he and Dylan spent the weekend doing brotherly things like riding bikes and throwing a football around.
"This is completely unreal," Sebastian said. "Healthy 12-year-old boy just gone. No family should feel the pain that we're going through right now."
Mike Medwin, the partner of Dylan's mother, said the Palm Beach County Medical Examiner told Dylan's father the findings of Dylan's death.
"It was an aggressive form of the flu," Medwin said.
Medwin said Dylan rarely got sick, had no underlying health issues, loved to play sports and displayed an intelligence and sense of humor well beyond his years.
He said the family heard about a deadly flu across the country but never expected it could hit them.
"You shrug your shoulders," Medwin said. "No way. We're healthy. The kid's playing soccer. He's strong."
Sebastian said his mother is in unimaginable pain. "Please stay on top of your babies," she wrote on Facebook. "It may look like a regular cold.. I refuse to let any parent go [through] what I'm going through."
"It's something that she can't grasp either," Roa said. "Something that she grieves about it, but at the same time we want to get awareness out there. We don't want him to die in vain."
Doctors said they're seeing a staggering amount of flu cases and that the flu often seems like a cold at the outset but it's more than that.
"You'll also have a headache and the symptoms tend to come on more suddenly, and where both can give you a fever, the fever from the flu tends to be much higher -- so above 101, maybe 102 or so," said Dr. Aileen Marty.
Doctors said the key is to get to a doctor within 48 hours of the first symptoms to get a medication like Tamiflu.
The family has set up a GoFundMe page to help pay for Dylan's funeral expenses. The family wants to also use the fund to help pay for medical expenses for those who can't afford it.
They want everyone to be aware that the flu can deadly and that they should take precautions.
"If you feel you have a sickness, you have a cold, you have a flu, whatever it is. If your child has it, whatever it is, get medical attention because this can happen to anyone," Sebastian said.