Hélène Pastor: Monaco's richest woman who developed her family's property empire but was shot dead in an ambush

Hélène Pastor was Monaco's richest woman, head of one of the principality's wealthiest families and a close friend of the Royal family there. She died of gunshot wounds after being caught in an ambush.

Pastor, known locally as "la vice-princesse", and her chauffeur, Mohammed Darwish, 64, were hit by a hail of bullets outside L'Archet hospital in Nice on 6 May. She had just finished a two-hour visit to her son, Gildo, the owner of a car-hire company, who was recovering from a stroke, when a gunman struck. Armed with a sawn-off shotgun he jumped out from behind a parapet and fired into the passenger side of her Lancia Voyager people carrier then escaped in a waiting car.

The gunman left Pastor with injuries to her face, neck, chest and abdomen, while Darwish sustained wounds to the face, neck and stomach. He died four days later. Pastor was taken to Nice's St Roch hospital and underwent several operations but died on 21 May.

Investigators believe the two suspects were members of one of Italy's most notorious crime syndicates, either the 'Ndrangheta or the Camorra. Both groups are thought to have gained a strong foothold in the French Riviera's property sector, in which the Pastor family are key players. Russian crime syndicates have not been ruled out. The principality's status as a tax haven means that it is regularly linked with organised crime gangs, as well as prominent individuals who want to keep the source of their wealth a closely guarded secret.

Born in 1937, Pastor was one of three children born to Gildo Pastor, who went on to make a fortune in real estate. The Pastors, however, came from humble beginnings. Her grandfather, Jean-Baptiste, was a stonemason from the coastal town of Liguria in north-western Italy who moved to Monte Carlo in the 1880s.

After a number of successful public works developments he was commissioned by Prince Louis II to build the principality's first football stadium, in 1936; his son Gildo then took over the business. This was the beginning of a prosperous and enduring association between the Pastors and the house of Grimaldi. After the Second World War Gildo accumulated substantial swathes of waterfront land very cheaply and began to build luxury apartments, which soon became sanctuaries for the world's rich and famous in search of ultra-low taxes combined with the Riviera's ostentatious lifestyle.

When Gildo died in 1990, his three children, Hélène and her late brothers, Michel, an art lover and former chairman of Monaco FC, and Victor, inherited his fortune. The Pastors continued to develop new properties and pursue interests in many other aspects of the local economy, with Hélène quietly managing her portfolio of five mansion blocks in prestigious addresses along the avenues Princesse-Grace and Grande-Bretagne, which she would rent out for about £12,500 per month for a four-bedroom flat.

The Pastors' property portfolio is conservatively worth an estimated £16 billion, comprising more than 3,500 out of the principality's total of 20,000 apartments in just two square kilometres.

Described by friends as a "model of wisdom and discretion", Hélène was somewhat reserved and did not crave the limelight, often avoiding the many grand and extravagant social events. She preferred walking her dog, managing her properties and re-investing her ever-increasing cash flows.

Baffled by the double murder, the anti-terrorist police are now looking into any family secrets that may have provided a motive. She was reported to have told police before she died that she knew of no one with a grudge against her.

Her son Gildo and her second husband, Professor Claude Pallanca, a prominent Monégasque dentist who was also the honorary consul of Russia, have refused to speak to the press. Pallanca commented, "Je ne veux pas avoir de problèmes." [I don't want any problems]. Pastor is survived by her daughter from her first marriage and her son.

Hélène Pastor, businesswoman: born 1937; married twice, divorced twice (one daughter, one son); died Nice 21 May 2014.