The Ventura County Medical Examiner released the full report along with the autopsy report, which details the “Glee” actress’ final moments after she assisted her 4-year-old son, who was later found sleeping alone on the vessel wearing a life vest, up onto the rental boat.
According to the investigative report, before the accidental drowning, Rivera's son Josey said he and the star "counted '1, 2, 3' and then jumped off the boat together."
Not too long after, Rivera told her son "to get back on to the boat," according to the report.
"She helped him onto the boat and he then heard [Rivera] yell 'help' and she put her arm in the air. She then disappeared into the water," according to the report.
Furthermore, the official autopsy report indicates Rivera, 33, “was considered to be a good swimmer,” and according to a lake attendant who rented her the boat, Rivera had declined a life vest, but he included one for her anyway.
In the report, the medical examiner determined via toxicology that Rivera had a small amount of prescribed amphetamines in her system, but did not identify physical conditions or drugs as factors in her death. She had previously dealt with vertigo problems and had a recent sinus infection, the conclusion revealed.
Toxicology tests also showed Rivera had small, trace therapeutic amounts of the anti-anxiety drug diazepam and the appetite suppressant phentermine in her system.
In addition, there was "no known history of suicidal ideation or attempt," according to the autopsy report.
Rivera's cause of death remains a drowning and her manner of death an accident, the report states.
On July 13, Rivera’s body was located five days after her disappearance floating in an area of the lake that is about 30 feet deep. The Ventura County Sheriff's Office said she was most likely trapped in thick vegetation underwater for several days before floating to the top.
Josey was immediately reunited with his father and other relatives.
The day before her death, Rivera tweeted a photo of the two of them that read, “just the two of us.” In her memoir, she called him “my greatest success, and I will never do any better than him.”
Rivera was laid to rest at Forest Lawn Memorial Park in Los Angeles two weeks after her death on Friday, July 24, according to a death certificate obtained by People magazine at the time.
The Associated Press contributed to this report.