Fort Worth, Texas — A Serbian competitor in the CrossFit Games has died while competing in a swimming event Thursday morning at a Texas lake.

CrossFit CEO Don Faul said during a news conference that they were "deeply saddened" and were working with authorities on the investigation into the death of one of their athletes at Marine Creek Lake in Fort Worth.

The Tarrant County medical examiner's office identified the athlete as 28-year-old Lazar Dukic of Serbia. The medical examiner's office had not yet listed his cause of death.

An official with the Fort Worth Fire Department said they were called out around 8 a.m. to assist police because there was "a participant in the water that was down and hadn't been seen in some point in time." Police said that officers who were working the event were told that a participant was unaccounted for after last being seen in the water and then not resurfacing.

The Fort Worth fire official said they responded for search and rescue and were not on the scene when the initial call was made.

Faul said CrossFit had a safety plan and did have safety personnel on site at the event. CrossFit did not respond Thursday to an inquiry from The Associated Press to provide more details on that safety plan.

The Fort Worth Star-Telegram reported that the event on Thursday included a 3.5-mile (5.6-kilometer) run followed by an 800-meter (0.5-mile) swim. The newspaper said an estimated 10,000 people were in the area for the games, which began Thursday and were set to run through Sunday.

Kaitlin Pritchard told the newspaper that she was standing by the finish line when she saw Dukic approach. She said he was among swimmers she'd noticed had changed up their swimming patterns, which she thought could have been because they were tired from the run.

Pritchard said she saw people she assumed were lifeguards on paddleboards on the lake, but she didn't notice that any of them jumped in to try to rescue anyone.

"Gauging where the people on the paddleboards were and everything, it's just that he should have been reachable," Pritchard told the newspaper.

The mission of the CrossFit Games, first held in 2007, is to "find the fittest athletes in the world," the CrossFit website said. It says the games change every year and often the details are not announced until just before the event.

Faul said the CrossFit community is like a family. "We're doing everything in our power during this tragic time to support the family, to support our community," Faul said.

Dukic's biography on the CrossFit website says he was the third-ranked CrossFit athlete in Serbia and the 88th-ranked worldwide. Dukic finished ninth in his debut in the games in 2021, then eighth the next season and ninth in 2023.