The son-in-law of the 77-year-old heiress of one of Monaco's richest families has admitted to involvement in her murder last month, reports RTE.
Wojciech Janowski, a 64-year-old who is also Poland's honorary consul in Monaco, "recognised his involvement" in the killing while in detention this week, Marseille prosecutor Brice Robin said.
Helene Pastor shot multiple times as she was leaving a hospital in the French Riviera city of Nice.
Her only daughter, Sylvie, and her husband, Janowski, were among 23 people detained in raids in Nice on Monday night.
Her driver, Mohammed Darwich, 64, also died from injuries sustained in the attack.
Mr Robin said police were also investigating "suspicious financial flows" in Mr Janowski's accounts.
He said two of the men being held, 31-year-old Alhair Hamadi and 24-year-old Samine Said Ahmed, had been identified as being "present at the location of the killing".
Read more of this report from RTE.