Angela Chao, the billionaire sister-in-law of Senate Republican Leader Mitch McConnell, was drunk when she died after her Tesla slowly sank in a pond on her sprawling Texas ranch, authorities say. 

A police report released on Wednesday called the incident an "unfortunate accident."

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.

She left her guests at the 10-bedroom house known as The Inn to return to the main house to be with her son, Chao.

A video from an outdoor security camera captured Chao at 11:37 p.m. walking "unsteadily to her vehicle while continuing to hold her cellular phone in her right hand," according to the report.

After getting in her car, Chao attempted to make a three-point turn, but tragedy struck.

A panicked Chao called a friend from the car 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.

She also said she was "going to die" and "I love you" before the car sank, the report claims.

The report, released by the Blanco County Sheriff's Office, described the chaos around the incident as friends responded and attempted to save her.

One person used a kayak to reach the vehicle and another person swam to the car. They climbed on top of it and tried to get to Chao in the car, according to the report.

Authorities reached the ranch shortly after midnight.

They broke the window of the car to reach Chao.

First responders pronounced her dead at 1:40 a.m.

Toxicology found that Chao's blood alcohol concentration was 0.233, according to CNN.