Beachgoers sensed trouble when a loud explosion echoed, sending a paraglider spiraling out of control and causing the tragic death of its sole flyer, extreme athlete Felix Baumgartner, as it crashed beside a swimming pool near the Adriatic Coast.

A 30-year-old mother observed the fatal fall unfolding Thursday afternoon while she was near the scene with her two young children, who were captivated by the frequent sight of paragliders above the beach town of Porto Sant’Elpidio in the Marche region of central Italy.

“Everything seemed fine until it began spinning like a top,” recounted Mirella Ivanov on Friday. “It went down, and we heard a loud noise. In fact, I turned around because I thought it had hit the rocks. Then I saw two lifeguards rushing, along with other people running towards the crash site.”

When she saw people trying to revive the occupant, she scurried her two children away.

The city’s mayor confirmed the death of 56-year-old Baumgartner, who was renowned as the first skydiver to fall faster than the speed of sound. The cause of the paragliding accident was under investigation. Police did not return calls asking for comment.

“It is a destiny that is very hard to comprehend for a man who has broke all kinds of records, who has been an icon of flight, and who traveled through space,” Mayor Massimiliano Ciarpella told The Associated Press.

Ciarpella said that Baumgartner had been in the area on vacation, and that investigators believed he may have fallen ill during the fatal flight.

Baumgartner’s social media feed features videos of him in recent days flying on a motorized paraglider —known as paramotoring — above seaside towns, and taking off from a nearby airfield surrounded by cornfields.

The Club de Sole Le Mimose beachside resort where the crash occurred said in a statement that an employee who was “slightly injured” in the accident was in good condition. No guests were injured, and the pool has been reopened.

In 2012, Baumgartner, known as “Fearless Felix,” became the first human to break the sound barrier with only his body. He wore a pressurized suit and jumped from a capsule hoisted more than 24 miles above Earth by a giant helium balloon over New Mexico.

The Austrian, who was part of the Red Bull Stratos team, topped out at 843.6 mph — the equivalent of 1.25 times the speed of sound — during a nine-minute descent. At one point, he went into a potentially dangerous flat spin while still supersonic, spinning for 13 seconds, his crew later said.

Baumgartner’s altitude record stood for two years until Google executive Alan Eustace set new marks for the highest free-fall jump and greatest free-fall distance.

In 2012, millions watched YouTube’s livestream as Baumgartner coolly flashed a thumbs-up when he came out of the capsule high above Earth and then activated his parachute as he neared the ground, lifting his arms in victory after he landed.

Baumgartner, a former Austrian military parachutist, made thousands of jumps from planes, bridges, skyscrapers and famed landmarks, including the Christ the Redeemer statue in Brazil.

In 2003, he flew across the English Channel in a carbon fiber wing after being dropped from a plane.

In recent years, he performed with The Flying Bulls, an aviation team owned and operated by Red Bull, as a helicopter stunt pilot in shows across Europe.

Red Bull paid Baumgartner tribute in a post Friday, calling him “precise, demanding and critical. With others, but above all toward yourself.”

The statement underlined the research and courage with which Baumgartner confronted “the greatest challenges.”

“No detail was too small, no risk too great, because you were capable of calculating it,’’ Red Bull said.