Naya Rivera and Son Counted '1,2,3' and Jumped in Lake Before She Yelled 'Help' and Drowned

Naya Rivera and Son Counted '1,2,3' and Jumped in Lake Before She Yelled 'Help' and Drowned

Naya Rivera's Cause of Death Ruled as Accidental Drowning

PLUS: Rivera’s ex Ryan Dorsey "can't imagine raising Josey without" her

Heartbreaking details surrounding the death of Naya Rivera have been revealed as the Ventura County Medical Examiner has released the Glee star's full autopsy and investigative reports.

According to the investigative report obtained by PEOPLE, Rivera's 4-year-old son Josey — whom she shared with ex-husband Ryan Dorsey — said that before the star disappeared into the water and drowned, they counted "1, 2, 3" and jumped off the pontoon boat together at Lake Piru in Ventura County, California, on July 8.

After getting into the water, Josey said his mother told him to get back on the boat, according to the report.

"She helped him onto the boat and then he then heard [Naya] yell 'help' and she put her arm in the air. She then disappeared into the water," the investigative report states.

Officials also noted in the investigative report that while Rivera was in good health, she had a history of vertigo "that would get worse when she was in the water."

naya rivera/instagram Naya Rivera and son Josey

RELATED: Naya Rivera's Cause of Death Ruled as Accidental Drowning

"The decedent would have vertigo to the point of vomiting, but she learned to control the symptoms with antihistamines," the report states.

Rivera had been treated at Cedars Sinai hospital for vertigo prior to her death.

Amy Sussman/Getty Images Naya Rivera

The investigative report also reveals that Rivera had been prescribed adderall for anxiety and was recently taking medication for a sinus infection. Additionally, Rivera "used a marijuana vape pen and she would smoke about a pack of cigarettes per week," the report states.

According to her autopsy report, Rivera had "no known history of suicidal ideation or attempt."

The actress was also "considered to be a good swimmer," the autopsy report states. Her cause of death remains a drowning and the manner of death was ruled as an accident.

Gregg DeGuire/Getty Images Naya Rivera and son Josey

The Ventura County Medical Examiner also released Rivera's toxicology report, which reveals the actress had low-level amounts of amphetamine (Adderall, Dexedrine), diazepam, ethanol and phentermine (an appetite suppressant) in her system, as well as caffeine, at the time of her death. According to the toxicology report, her blood alcohol concentration was 0.016.

"[Naya's] cell phone, syringes with a pink fluid substance, identification, and a filled prescription slip for amphetamine was found in [her] purse. Three 12 ounce White Claw alcohol cans were located near [her] purse. One of the cans was empty, one was open and was about 3⁄4 full, and one was unopened. There was a bag with food items on a bench seat near the front of the boat," the investigative report states.

Rivera was confirmed dead on July 13 at the age of 33 — five days after she disappeared. She was reported missing after renting the pontoon boat with her son.

When the boat became overdue for return after its three-hour rental, staff found it at the north side of the lake, with Josey wearing a life jacket, sleeping alone on board. An adult life jacket, believed to be the one provided to Rivera, was still on the boat. One day later, police announced she was presumed dead, maintaining they considered her disappearance to be "a horrible accident."

FOX Image Collection via Getty Images Naya Rivera in Glee

Authorities searched the waters with the help of dive teams and sonar technology for days, but the murky conditions of the lake complicated their efforts. On Monday, July 13, the Ventura County Sheriff's Office tweeted that a body had been found in the lake.

RELATED: Naya Rivera Laid to Rest 2 Weeks After Drowning, Death Certificate Reveals She Died Within Minutes

"We are confident the body we found is that of Naya Rivera," Ventura County Sheriff Bill Ayub said in a news conference. "It has been an extremely difficult time for her family throughout this ordeal ... our hearts are with them and we share in their grief for Naya’s loss."

Lake Piru has been the site of several drownings over the years, and the actress' disappearance prompted a petition calling for signs warning swimmers of its dangerous conditions.

"He and Naya swam in the lake together," Ayub said of Rivera and her son. "It was during that time that her son described being helped onto the boat by Naya. ... He told investigators he looked back and saw her disappear under the surface of the water."

naya rivera/instagram Naya Rivera and her son, Josey, swimming on July 4, 2018

Ayub later added, "We believe that she mustered enough energy to get her son back on the boat, but not enough to save herself."

Rivera was buried at Forest Lawn Memorial Park in Los Angeles on July 24, according to her death certificate, which was obtained by PEOPLE.

The document, filed in Ventura County, confirms that Rivera's cause of death was "drowning" and states that she died within a matter of "[minutes]."