Tributes are pouring in after a beloved member of Monaco’s royal family died suddenly over the weekend.

Prince Albert II, the leader of the European principality of Monaco, revealed on Monday that his cousin Antoine de Massy unexpectedly passed away on Sunday night.

He was just 29 years old.

The 68-year-old prince, who has led the country since 2005, publicly addressed the tragic loss in a joint statement with his wife Princess Charlene.

“Their Serene Highnesses Prince Albert II and Princess Charlene were saddened to learn of the death of Antoine de Massy, aged 29, the grandson of Princess Antoinette, the elder sister of Prince Rainier III,” a statement released on behalf of the Monaco leader on Monday read.

“Their Highnesses share in the grief of his family and loved ones, and offer them their sincere condolences at this painful time.”

It is understood concern over Antoine de Massy’s whereabouts first began on Sunday, when the 29-year-old failed to attend a family lunch.

The royal family contacted Monaco’s Public Security department, who reportedly discovered the young man’s body in a garden behind Villa Sauber, a cultural landmark in the European principality.

Monaco’s prosecutor general told local news outlet Monaco-Martin that an investigation has been opened to determine Mr de Massy’s cause of death.

Prince Albert II described his late cousin as a “a keen tennis player” who played an important role in the nation’s ties to the sport.

Antoine began playing tennis at age three and later moved to Florida to train in the sport while attending school.

He had previously told Vogue Italia in 2012 that he hoped to represent Monaco at the Olympics for the sport, with the royal also dreaming of becoming number one in the world.

Antoine’s love for the sport was in his blood — with the late athlete’s aunt Elizabeth-Ann de Massy acting as the leader of the Monegasque Tennis Federation until her passing in 2020.

Her daughter Melanie-Antoinette de Massy — Antoine’s cousin — is now running the federation as well as the Rolex Monte-Carlo Masters.