Arlington man, 46, dies while competing in Ironman competition in Galveston, Texas

An Arlington man who died Sunday morning while competing in an Ironman competition in Galveston, Texas, was remembered by friends and family as a loving father and an accomplished engineer and leader.

Daniel Winkler, 46, was pronounced dead at an area hospital about an hour after he was pulled from the water during the swim portion of the Ironman, officials said. The competition includes swimming, running, and cycling courses.

Winkler was vice president of software engineering at 6 River Systems in Waltham, a warehouse solutions company that develops technology to facilitate order fulfillment. Winkler was married, and he and his wife, Regan, had two daughters, ages 6 and 8, according to his sister-in-law, Erin Dillon.

“We are in shock and trying to comprehend Dan’s death,” his family said in a statement Monday. “His positive energy, love for his family, and drive to harness all that life could offer is truly irreplaceable. We want him remembered for his life: his big hugs, infectious laugh, and radiant smile. He made everyone feel like family and he will be missed by countless friends, family, and coworkers.”

Lifeguards spotted Winkler about four inches underwater “in the middle of a lot of swimmers and kayakers” providing security as athletes swam through the water in Offatts Bayou, according to Galveston Island Beach Patrol Chief Peter Davis. Winkler was “about halfway through the swim” portion of the 70-mile course, Davis said.

Rescuers immediately began providing CPR to Winkler, with medical aid continuing as the athlete was taken to a local hospital, where he was pronounced dead about 9:30 a.m. Sunday, Davis said.

“They basically did CPR for about an hour,” Davis said of the initial rescuers who tended to Winkler before his arrival at the hospital.

The county medical examiner’s office will issue a formal cause of death. John Florence, chief investigator with the office, said Monday that the cause remained pending, though “it doesn’t appear to be drowning at this time.”

On its Facebook page, the Ironman 70.3 Texas event also confirmed the death of Winkler without mentioning him by name. The race includes a 1.2-mile swim, a 56-mile bicycle portion, and a 13.1-mile run.

“During the swim portion of the Ironman 70.3 Texas triathlon, an athlete required and received medical attention upon swim safety personnel recognizing the athlete was in need of assistance,” the posting said. “The athlete was transported to a nearby hospital, where we were saddened to learn [he] passed away. We share our greatest sympathies with the family and friends of the athlete and will continue to offer them our support as they go through this very difficult time.”

Christopher Cacioppo, chief technology officer and co-founder of 6 River Systems, said he worked with Winkler on and off for 23 years and described him as “an incredibly brilliant engineer and technical leader.”

They previously worked together at Cambridge-based Mimio before it was acquired by Boxlight in 2016. Winkler, who is originally from the New Orleans area and graduated from Northeastern in 1999, worked at Mimio for 16 years before joining 6 River Systems in 2016, according to a LinkedIn page in his name.

“Whether researching learning techniques, robotics, encryption, or any task at hand, Dan had the amazing talent of quickly and deeply researching topics and distilling their essence,” Cacioppo said in a statement. “Dan also strove for simplicity, and finding clean simple solutions to complicated problems. Dan was amazing to work with, becoming personal friends with many of his colleagues.

“Last, but certainly not least, he was a great mentor — always helping make the people around him better. Although he will be missed first as a friend to many, his contributions to technology and to his teams will also be a tremendous loss.”

Rylan Hamilton, co-founder and co-chief executive of 6 River Systems, said Winkler was one of the company’s first employees, “and his immense contributions will forever be part of our DNA.”

“He accelerated the trajectory of the company and his enthusiasm was infectious. Dan was a rare force in this world, and just as kind as he was brilliant. We will miss him dearly and our thoughts are with his family,” Hamilton said in a statement.