The father of four children killed in a horrifying murder-suicide in upstate New York has spoken publicly about the devastating details revealed by a newly released toxicology report.

Brady Harmon said it was “sickening” to learn that his children may have endured unimaginable suffering before their deaths. His children — 13-year-old Harper, 11-year-old Hudson and 10-year-old twins Gavin and Gracelynn — were found dead alongside their mother and grandmother in a Mechanicville apartment in June.

Authorities believe the children’s mother, 44-year-old Sarah Myers, and their grandmother, 64-year-old Amy Steadman, were responsible for the killings before taking their own lives. Police have described the children’s deaths as homicides.

Toxicology Reveals Drug Combination

A toxicology summary released by Mechanicville police showed that all six deceased family members had diphenhydramine in their systems at fatal or lethal levels. Diphenhydramine is an antihistamine commonly found in over-the-counter allergy medications such as Benadryl.

Four of the six — including the children — also had mitragynine, the primary active compound in kratom, in their systems. Kratom is a plant-derived substance that the U.S. Drug Enforcement Administration classifies as a “Drug and Chemical of Concern.” At high doses, it can produce sedative effects and opioid-like effects.

Police have not released individual toxicology reports showing exactly which combination each person received. However, investigators confirmed that Gavin, who had also suffered fatal stab wounds, had been poisoned as well.

Police Say the Deaths Were Planned

The six family members were discovered inside Steadman’s apartment on June 23 after neighbors became concerned that they had not seen the family and reported suspicious odors.

Investigators later determined that the killings had occurred around June 10. Police said text messages between Myers and Steadman indicated that the two women had been discussing how to administer medication to the children.

Investigators also found handwritten notes that appeared to describe the women’s reasons for killing the children. According to police, the notes referenced allegations of abuse involving the children’s father, who lived in Utah.

Authorities said they found no evidence substantiating those abuse allegations. Harmon has denied them.

Police also said Gavin suffered multiple stab wounds and defensive injuries, indicating that he may have attempted to protect himself during the attack. Investigators found searches on Steadman’s devices concerning potentially fatal stabbing locations and other methods of causing death.

Father Was Preparing to See His Children

The tragedy was particularly devastating for Harmon because he had been preparing to reunite with his children.

Harmon and Myers had separated in 2019. According to Harmon, he had spent years attempting to establish custody or visitation and was scheduled to have the children stay with him in Utah beginning July 1 — their first in-person parenting time with him in more than six years.

In messages exchanged shortly before the killings, Myers told Harmon that the children had a “little stomach bug” and asked to postpone a scheduled video call. Harmon later shared those messages publicly, saying nothing in the conversations warned him about what was allegedly happening behind the scenes.

He ultimately learned that his children had died before he could see them again.

‘My Kids Suffered’

After learning more about the toxicology findings, Harmon shared his grief publicly.

The newly revealed evidence has intensified his anguish because it suggests that the children were given potentially lethal substances before they died. The father said the knowledge that his children may have suffered during their final moments was especially difficult to comprehend.

The case has shocked Mechanicville, a small community located about 18 miles north of Albany. Police have continued to investigate the circumstances surrounding the deaths, including the planning, the medications obtained before the killings and the handwritten statements left behind.

Authorities have characterized the killings as a murder-suicide and said there is no evidence that an outside perpetrator was involved.

For Harmon, however, the investigation cannot undo the loss of four children he had hoped to see again.

Harper, Hudson, Gavin and Gracelynn were just days away from what their father had hoped would be the beginning of renewed time together. Instead, their lives ended in a tragedy that has left their family and community searching for answers.

Sources: New York Post; PEOPLE; ABC News; CBS6 Albany (WRGB); Mechanicville Police Department; NewsChannel 13; Times Union.