Jonah Shacknal's son Max died after falling down stairs at the same house where the tycoon's girlfriend was found dead, hanging nude from a balcony
Police are attempting to get to the bottom of what they described as two "bizarre" deaths that occurred within 48 hours of each other at the historic seaside home of one of the wealthiest men in San Diego.
Jonah Shacknai, the founder and chief executive of a pharmaceutical corporation called Medicis, announced on Sunday that his six-year-old son, Max, had died from injuries suffered during a fall down the "grand staircase" of Spreckels Mansion, his 27-room house in the upmarket suburb of Coronado.
Two days after the child was taken to hospital, the body of Mr Shacknai's girlfriend, Rebecca Nalepa, was found hanging from a balcony in the main courtyard of the property. She was naked, with a rope around her neck; investigators told the media that her hands and feet were bound tightly.
Mr Shacknai, 54, was apparently not at home during either incident, which occurred last Monday and Wednesday. Police have yet to establish a link between the two deaths and are working to determine whether Ms Nalepa died as the result of a homicide or suicide.
No suspects have yet been named in either case, but Tim Curran, with the local sheriff's department, stoked public interest by telling NBC News that the possible events that saw 32-year-old Nalepa meet her end are being regarded as "very suspicious" and "violent". The "circumstances are bizarre", he said. "It appears to be some type of a violent death and I'm not going to compromise the integrity of the investigation by giving anything more than that at this time."
Mr Shacknai, who has divorced twice, made his fortune selling products such as the acne treatment Solodyn and Dysport, a wrinkle cream regarded as a competitor to Botox. His firm made $700m (£440m) last year. Its share price has fallen around 5 per cent since news of the deaths emerged, but it retains a market capitalisation of more than $2bn.
Spreckels Mansion is a well-known local landmark built in 1908 by one of the city's first tycoons, John D Spreckels. Mr Shacknai bought the mansion three years ago. Ms Nalepa, who was once convicted for shoplifting from a luxury-goods store, moved in during 2009 and was apparently looking after Max at the time of his fatal fall.