COLLEYVILLE (CBSDFW.COM) – The flu virus killed a 27-year-old man who friends say was the picture of health.

Jeremy Westerman coached health and fitness at 24-Hour Fitness, choosing a profession in personal training as a way to give back. “He said, ‘Dad, this is another way of me helping other people. I want to help people, and I know I can,'” recalled Jeremy’s father, Marty Westerman.

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Jeremy Westerman, 27 (photo courtesy: Twitter)

Jeremy’s parents said he began feeling lethargic and nauseated a few months ago. On January 2, he became violently ill and went to bed after spiking a high fever.

Westerman never woke up.

“As a parent, that’s a major shock. This is something we did not expect,” said Marty Westerman.

The family learned this week that Influenza A (H1N1) was the cause of death, with a secondary cause of an adrenal insufficiency that likely made Jeremy susceptible to the virus.

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“I just felt like it was just… like a senseless death,” said mom Diana.

“He was in such good health. He was a trainer. He worked out all the time. And for it to take him like it did, it’s absolutely terrifying,” said Marty Westerman.

And while they still struggle to understand how and why, they know their son maximized the time here he had.

“It’s amazing what this 27-year-old has done in such a short time. And I thank the lord for allowing me to have 27 years with this kid,” his father said.

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His parents tell CBS11 he did have a flu shot back in October. He is the 12th person to die from the flu in Collin County this season.