BOISE -- A Boise woman intentionally steered her SUV off a cliff into Lucky Peak last year, killing herself and her three children, Ada County Sheriff's Office investigators have found.

The horrific crash happened June 2, 2016. Forty-year-old Noel Bankhead and her children - 13-year-old Anika Voermans, 11-year-old Logan Voermans and 8-year-old Gwyneth Voermans - all died from drowning associated with blunt force trauma.

The investigation into the crash stretched on for more than a year. The sheriff's office announced Friday that investigators have concluded that Bankhead purposefully drove her Land Rover off the sharp dropoff on the side of East Spring Shores Road, near the Idaho 21 bridge over Lucky Peak, commonly known as the High Bridge.

The SUV plummeted more than 50 feet before it hit the water, investigators say. The vehicle quickly sank to the bottom of the reservoir.

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Witnesses to the crash said that Bankhead was driving north on Idaho 21 at about 7 a.m. when she slowed down, turned onto Spring Shores Road, pointed the SUV toward the cliff, and suddenly accelerated off the edge.

No skid marks or indication of braking was found. Investigators also found no evidence of mechanical problems with the SUV.

The children's deaths were ruled homicides, while their mother's death was a suicide, officials say. A motive in the intentional crash is unclear.

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Bankhead's autopsy revealed that she had no alcohol or medication in her system at the time.

Investigators attempted to retrieve information from the Land Rover's water-damaged Event Data Recorder (EDR) - which measures things speed, braking, acceleration, and fault codes - but were unsuccessful, even though the sheriff's office twice sent the device to Land Rover’s European offices for analysis.

Logan, Anika and Gwyneth attended East Junior High and Riverside Elementary School in Boise, according to school officials. After the deadly crash, mourners left flowers and other tributes near the spot where the Land Rover had gone off the cliff.

Authorities placed several large boulder along the dropoff after the crash, to prevent other drivers from going over.