SAN DIEGO — The 6-year-old son of a pharmaceutical executive died yesterday, almost a week after falling down the stairs at his father’s mansion — where the man’s girlfriend was found dead, hanging nude from a balcony, two days later.

Max Shacknai died at Rady’s Children’s Hospital in San Diego, Medicis Pharmaceuticals Chairman and Chief Executive Jonah Shacknai said in a statement with his ex-wife, Dina Romano, the boy’s mother. Last Monday, Max fell down the stairs at the Spreckels mansion in Coronado in what police called an accident.

On Wednesday, Shacknai’s girlfriend, Rebecca Nalepa, 32, was found hanging from a balcony there, her hands and feet bound. Shacknai’s brother, who was staying in the guesthouse, called to report Nalepa appeared to be dead, police said. Jonah Shacknai, 54, was not at home.

Sheriff’s Capt. Tim Curran has called the death “very bizarre.”

Police have not established a connection between the two deaths, and have not determined if Nalepa was a crime victim. They said they have not ruled out suicide.