CORONADO, Calif. -- Coronado police have rejected a request by the mother of a 6-year-old boy who died after falling down stairs at a California mansion to reopen the investigation into her son's death.

U-T San Diego reports (bit.ly/RAaX94) that representatives of Dina Shacknai released a letter from Coronado's police chief and San Diego County's chief medical examiner that reaffirmed Max Shacknai's death was an accident.

The younger Shacknai plunged over a stairwell banister at his father's mansion in July 2011 and died from brain injuries. His father's girlfriend killed herself two days after the fall.

Investigators say the boy may have tripped while running, grabbed a chandelier, hit his back on the banister and fallen. Dina Shacknai hired an expert who said her son's death was likely the result of an assault.

Earlier on HuffPost:

Loading Slideshow...
  • Flowers and messages adorn a flower box outside the Spreckels Mansion in Coronado, Calif. Monday, July 18, 2011. The mansion is the site where a woman was found dead July 13, she was hanging nude from a balcony with her hands and feet bound. Credit: Lenny Ignelzi, AP

  • This 2010 photo released by Medicis Pharmaceuticals Corp. shows CEO Jonah Shacknai. Shacknai's 6-year-old son and 32-year-old girlfriend have each died in a span of less than a week, and both deaths were tied to his historic mansion on the San Diego Bay. Credit: Medicis Pharmaceuticals Corp. / AP

  • This August 2008 photo released by Horizon Eye Specialists & Lasik Center shows Rebecca Zahau, also known as Rebecca Nalepa, 32. Nalepa, the girlfriend of Arizona pharmaceuticals tycoon Jonah Shacknai, was found dead last week hanging nude from the second-floor balcony of a historic mansion, her wrists and ankles bound. Credit: Dwight Smith, Horizon Eye Specialists & Lasik Center / AP

  • This photo family released on Sunday, July 17, 2011 shows his 6-year-old Max Shacknai. Shacknai, son of Medicis Pharmaceuticals CEO Jonah Shacknai, has died, almost a week after falling down the stairs at his father's San Diego-area mansion, the same house where his father's girlfriend was found dead hanging nude from a balcony two days later. Credit: Family Photo / AP