Missouri firefighter’s doctor girlfriend died of multiple drug intoxication, manner ‘undetermined’

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A 39-year-old doctor found dead with no “obvious” signs of trauma in her boyfriend’s home in suburban St. Louis died of a drug overdose, police said Tuesday evening, citing a toxicology report.

Dr. Sarah Sweeney’s death on Jan. 13 is the second death of a woman in the home of Robert Daus, a Maryland Heights firefighter.

Frontenac police said her cause of death was “Oxycodone, Gabapentin, and Diphenhydramine intoxication.” The manner of death remains undetermined – leaving open the possibilities that her death was an accident, a suicide or involved foul play.

“She died of an oxycodone overdose,” said Dr. Michael Baden, a prominent forensic pathologist and former New York City medical examiner. “The other two [drugs] don’t really cause many overdose deaths.”

MISSOURI FIREFIGHTER’S FIANCEE AUTOPSY REVEALS ‘SUSPICIOUS’ SCENARIO, EXPERTS SAY

Dr. Sarah Sweeney, left, and Grace Holland were found dead in homes belonging to Robert Daus. (Sweeney Family | Grace Holland/Facebook)

Daus called 911 in July 2020 to report his then-fiancee Grace Holland, 35, shot herself in the head.

Investigators have deemed Holland’s death a suicide and have not accused Daus of wrongdoing – but her family has named him in a wrongful death lawsuit. She was right-handed, but the gunshot struck her in the left temple, which her family says is suspicious, along with the disappearance of her $20,000 engagement ring.

Sweeney’s death cast renewed scrutiny over Holland’s case, which had already been under review by county police, who sent their findings to the St. Louis County Prosecuting Attorney’s Office in December.

Dr. Sweeney was in palliative care in December and was embroiled in a civil lawsuit against a former employer.

2 MISSOURI WOMEN FOUND DEAD IN SAME FIREFIGHTER’S HOME YEARS APART

Robert Daus in front of his home in Westwood, Missouri, on Jan. 29, 2024. Daus’ girlfriend, Dr. Sarah Sweeney, was found dead in his home on Jan. 13. Daus also lost his fiancee Grace Holland in another house three years ago of an apparent self-inflicted gunshot wound to the head. (DWS for Fox News Digital)

She had mast cell activation syndrome, a potentially life-threatening condition. Her mother, Teresa Sweeney Light, previously told Fox News Digital that the doctor had it under control with medication and carried an EpiPen.

The Frontenac Police Department, which is handling the Sweeney case, said their investigation is far from complete and that detectives are awaiting results for a number of other items.

Oxycodone is an opioid painkiller. Gabapentin is an anticonvulsant used to treat epilepsy patients and nerve pain, but Dr. Baden said it has many other uses. Diphenhydramine is the main ingredient in the allergy medicine Benadryl and also over-the-counter sleep aids. 

“So what would be important is what the drug levels are in the toxicology report,” Dr. Baden told Fox News Digital. “However, the drug out of the three drugs, the one that would cause 98% of the deaths, would be oxycodone.”

Grace Holland’s 2020 shooting death was deemed a suicide, but her family has disputed the findings. They filed a wrongful death lawsuit against Robert Daus, and the case has received renewed attention after Sarah Sweeney was found dead in his home in January. (Grace Holland/Facebook)

Police said they believe Sweeney was home alone prior to her death.

Sweeney’s family told Fox News Digital in January that she stopped communicating with her mother and stepfather after they sent her news stories about Holland’s death.

Holland’s family has claimed that the firefighter, a captain in the Maryland Heights Fire District, controlled her finances and that they suspected domestic violence in the months before her death.

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The home of Robert Daus in Westwood, Missouri, on Jan. 24, 2024. Two of Daus’ girlfriends have been found dead in homes belonging to him within the last three years. (DWS for Fox News Digital)

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Creve Coeur, Missouri, police handled the Holland case. Chief Jeffrey Hartman has stood by his department’s investigation but acknowledged that he would “expect increased scrutiny” if Sweeney’s case involves foul play.

Michael Ruiz is a reporter for Fox News Digital. Story tips can be sent to michael.ruiz@fox.com and on Twitter: @mikerreports