The doctor girlfriend of a Missouri fire captain died from a lethal cocktail of drugs at his home – three years after his fiancé was found shot dead.

Dr. Sarah Sweeney, 39, was found dead in the home of her fiancé, local fire captain Robert Daus, in suburban St. Louis on January 13. Oxycodone, the seizure and pain medication Gabapentin and antihistamine Diphenhydramine were found in Sweeney’s system.

On Tuesday, a toxicology report from the St. Louis County Medical Examiner’s Office revealed the doctor’s cause of death was drug intoxication, but the manner remains undetermined. 

‘Dr. Sweeney was found with no obvious signs of trauma discovered on her body, and our investigation, at this point, supports that she was home alone leading up to her death,’ the Frontenac Police Department stated. 

She is the second woman engaged to Daus who has died in recent years. Grace Holland was found dead in 2020 from a gunshot. Her death was initially ruled a suicide, but the investigation into Holland remains ‘active,’ authorities said. 

A toxicology report from the St. Louis County Medical Examiner’s Office revealed Dr. Sarah Sweeney’s cause of death was ‘Oxycodone, Gabapentin, and Diphenhydramine intoxication.’ However, her manner of death was ruled ‘undetermined’

Sweeney, 39, was found dead in the home of her fiancé, local fire captain Robert Daus (pictured), in suburban St. Louis on January 13

Sweeney was the second woman to have died when living with and engaged to Daus. Grace Holland (right) died from a gunshot wound to the head on July 22, 2020 at Daus’ home

Following Sweeney’s death, police reopened the investigation into Holland’s July 2020 death and their probe ‘remains active.’ 

Daus, a captain at the Maryland Heights Fire Department, has yet to be named a suspect in either case and has denied any involvement in their deaths.

Born in West Virginia, Sweeney moved to Missouri to open up her own podiatry practice in Creve Coeur.

Her mother, Teresa Sweeney Light, said: ‘We just wish we could have her back. We just want closure, we want it to be truthful and fair, and as of right now, we’re still in shock.’

According to her mother, Daus and Sweeney met when she was working an emergency room shift shortly after she moved to St. Louis.

‘Sarah was a vibrant and outgoing person who never, ever met a stranger. She loved dogs and cats, and she rescued and owned several over the years,’ said her obituary.

‘Sarah was diagnosed with Perthes Disease when she was six years old, which caused her to experience much physical pain throughout her life.’

Federal court filings reviewed by DailyMail.com, have revealed that Sweeney lived in fear of Daus and described him as ‘suspected of murdering a previous girlfriend.’ 

Sweeney’s claims surfaced in court filings that are part of a suit she brought against her former employer Best Foot Forward and its founder Dr. Franklin Harry in November 2022. 

Federal court filings reviewed by DailyMail.com, have revealed  Sweeney lived in fear of Daus and describe him as ‘suspected of murdering a previous girlfriend’

Following Sweeney’s death, police reopened the investigation into Holland’s death and their probe ‘remains active’

Sweeny emailed a friend: ‘But guess what Danielle? I’ve been homeless, I have had to move in with my boyfriend the ‘murderer’ which has been scary at times, I’ve lost every penny and closed out my savings account, I have had issues getting a job bc of my past affiliation with him, I have suffered…I have been through the ringer.’ 

Holland’s family have brought a wrongful death lawsuit in which they allege Daus is liable for Holland’s death and that he was psychologically and physically abusive.

Daus has never been charged in connection with Holland’s death which was ruled a suicide by the medical examiner despite several key factors that, her family say, contradict this finding.

They point out that Holland was right-handed and as a woman trained to use firearms had always shot with her dominant hand.

Yet she was shot in the left temple – a fact described by her family as ‘inconsistent’ with a self-inflicted wound and ‘consistent’ with someone standing opposite and shooting her.