CAPE MAY, N.J. (CBS) – The Philadelphia Fire Department is mourning one of its own. Off-duty firefighter Dennis McDaniels died Sunday while competing in a triathlon down the shore.

“Denny was a class act. In this firehouse, you just enjoyed being around Denny,” Philadelphia Fire Department Ladder 15 Lt. Michael Foley said.

McDaniels’ locker at Ladder 15 in Frankford is now empty after he died while competing in a triathlon in Cape May on Sunday morning. According to the Delaware River and Bay Authority, McDaniels was almost finished with the swimming portion of the Escape The Cape Triathlon when he was found unresponsive from an apparent cardiac arrest.

Medics performed CPR on the off-duty firefighter, but they were unsuccessful.

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Foley was there during the triathlon.

“We did the triathlon yesterday, the whole group from the station. Dennis has done it four years prior to this and this was the first time he did the Olympic one and that’s what happened yesterday,” Foley said. “He was swimming and he had the medical problem. We’re not sure exactly what happened but we were all there, but for us, we’re going to remember the day before, we had a great time.”

A 12-year veteran, McDaniels won a heroism award a few years ago, Foley says, after McDaniels rescued two women from a burning home near Frankford Avenue and Sellers.

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Although the news is unbearable for McDaniels’ wife and four young kids and colleagues, his lieutenant is proud of the times he spent with McDaniels.

“I’ve never been around a more happier person and he never was stressed. Even having four young children at home, nothing bothered him and to be around someone like that, just a joyful person, it was a pleasure to be around him and I’m going to miss him greatly,” Foley said.

A medical examiner in Somerset, New Jersey is conducting an autopsy Monday. The firefighters are working to create a scholarship fund for McDaniels’ four sons.

CBS3’s Chantee Lans reports.