​Angela Chao, the billionaire sister-in-law of Senate Republican Leader Mitch McConnell, spent her final moments making frantic calls for help to friends as her Tesla slowly sank in a pond on her sprawling Texas ranch, according to a report.​

Chao, 50, the CEO of global shipping empire Foremost Group and the sister of former Transportation Secretary Elaine Chao, had just left friends celebrating the Chinese New Year at a guesthouse on the 900-acre property outside Austin when she accidentally backed the Tesla Model X SUV​ into the water around 11:30 p.m. Feb. 9, the Wall Street Journal reported Saturday.

Moments after leaving her guests at the 10-bedroom house known as The Inn to return to the main house to be with her son, Chao attempted to make a three-point turn, but tragedy struck.

Chao, panicked, called a friend to say that she had put the car in reverse instead of drive, a mistake she had made before with the electric vehicle's gearshift.

The Tesla suddenly shot backward, went over an embankment and landed in the pond. It was sinking fast.

The call set off a frenzied attempt to rescue her, as the ranch manager and his wife, paramedics, firefighters and sheriff's deputies scrambled to break the windows in the submerged car.

They were racing against the clock. 

The report said a driver has approximately one minute to get out of a sinking car. 

In cars like the Tesla Model X, a driver might have only precious seconds to press the button to lower the window before the water level rises too high.

At that point, the only way to get out would be to break the window, auto safety experts told the news outlet.

After the call, Chao's friends rushed to the scene, and one of them jumped into the water.

The ranch manager arrived with his wife.

Someone called 911.

The first emergency unit from Blanco County arrived in 24 minutes, at about 12:28 a.m.

Because of the location, some first responders got out of their vehicles and hiked to the pond.

A deputy said the car was submerged and deputies were standing on its roof trying to break into the vehicle.

Rescue workers said they needed a dive team, but one wasn't available.

A tow truck arrived, but its cable wasn't long enough to stretch to the car.

Another tow truck driver was afraid of being electrocuted.

When the Tesla was finally pulled from the pond, hundreds of gallons of water poured out. 

Chao was unresponsive. Attempts to revive her were unsuccessful, according to Ben Oakley, the emergency services chief of Blanco County.

The Sheriff's Office, citing the continuing investigation, said it could not provide more information, but said a preliminary investigation indicated it was "an unfortunate accident."

The family doesn't blame Tesla, according to the report. Chao and her husband, venture capitalist Jim Breyer, have three Teslas.

Tesla did not respond to requests for comment from the Wall Street Journal.