Authorities are also continuing their investigating into the bizarre death of mansion owner Jonah Shacknai's girlfriend in the same historic Ocean Boulevard manor just two days after his son was gravely injured.

Shacknai, founder of Scottsdale, Ariz.-based Medicis Pharmaceutical Corp., has not spoken publicly about his girlfriend's death but issued a statement Sunday regarding his son:

"With great sadness, Dina and I convey the tragic passing of our beloved son, Max (affectionately known as Maxie). Despite heroic efforts on the part of paramedics and hospital staff, he was unable to recover from the injuries suffered early last week. His loving, kind and vibrant spirit will forever be in our hearts and those whom he touched every day. The loss to our families, Max's many friends of all ages and teammates, and the community is immeasurable.

We appreciate your respecting the privacy of our families during this time of grieving for Max. A private memorial service is being planned.

Memorial contributions honoring Max may be made to Whispering Hope Ranch Foundation either by mail to 9045 E. Pima Center Parkway, Scottsdale, AZ 85258, or via their website, www.whisperinghoperanch.org .

On behalf of Dina, myself and our families, please know of our appreciation for the tremendous outpouring of support provided during this very difficult time."

Last Monday morning, officers and medics responding to 911 call made by a woman at the estate found the child unconscious, without a pulse and not breathing, Coronado police said.

Authorities said the boy was seriously injured in a fall down a stairway at the home.

The boy's mother, Dina Shacknai, lives a short distance from the historic estate owned since 2007 by her ex-husband, who is chief executive officer of Scottsdale, Ariz.-based Medicis Pharmaceuticals.

Last Wednesday morning, Jonah Shacknai's brother, Adam, called 911 to report he had discovered 32-year-old Rebecca Zahau critically injured at the home. Police officers arrived to find Zahau lifeless on a lawn behind the 27-room main residence on the property.

Medics tried in vain to revive the naked woman, whose ankles and wrists were bound, before pronouncing her dead at the scene, sheriff's homicide Capt. Tim Curran told reporters. Coronado police then requested assistance from sheriff's homicide investigators, since the small peninsula city does not employ its own.

Adam Shacknai told investigators he found Zahau hanging from a second-floor bedroom balcony over a central courtyard and cut the rope or cord attached to her neck to get her down, Curran said.

Jonah Shacknai, Zahau's boyfriend, was not at the estate when the death was reported, Curran said. The captain declined to discuss the wealthy executive's whereabouts at that time or in the hours that followed, though he said investigators had been "in constant contact" with him since the start of the investigation.

Curran said it was not immediately clear if Zahau was slain or if she might have committed suicide in a novel way. In light of that uncertainty, the Shacknai brothers were considered witnesses, not suspects or even "persons of interest," the captain said.

"Because of the unique and bizarre circumstances of this incident, it has yet to be determined if this will become a criminal matter or will remain as a death investigation," Curran told news crews Thursday during a briefing at sheriff's headquarters in Kearny Mesa.

Despite the many unknowns in the lurid case, authorities said they were confident the woman's death was "an isolated incident" -- not the act of an unidentified killer who remained at large.

Zahau had been staying in the mansion with Jonah Shacknai, whose brother was a guest in one of the smaller residences on the grounds. The latter apparently was the only other person at the estate with the woman at the time of her death, Curran said.