The father of four children who were killed by their mother and grandmother in a horrific murder-suicide has said that their suffering prior to death was ‘unimaginable’ — and it was ‘sickening’ to know what they went through.

Harper Harmon, 13, Hudson Harmon, 11, and 10-year-olds Gavin Harmon and Gracelynn Harmon, were found dead at a home in Mechanicville, New York, on June 23 alongside the bodies of their grandmother Amy Steadman, 64, and 44-year-old mother Sarah Myers.

Their dad Brady Harmon, whom they had been due to spend the summer with in Utah, has now spoken out after toxicology reports revealed the children were poisoned with a combination of allergy medicine and kratom — a psychoactive herbal extract which is sold as an energy booster and pain reliever due to its opioid-like effects.

Speaking in a heartbreaking Facebook post Harmon wrote: ‘I will never understand how two people who claimed to love and care about these children could deliberately cause them such unimaginable harm.

‘The pain is still as raw as if it happened yesterday. Reading today’s official toxicology findings makes it even more sickening to understand what was done to them.’

Harmon has since moved to New York and, according to the New York Post, plans to sue authorities there for upwards of $400m amid claims that his children were killed following a pattern of abuse which continued under their noses for years.

The lawsuit is against the City of Mechanicville, Ballston Spa Central School District, Mechanicville City School District, Saratoga County, and the Mechanicville Housing Authority.

It’s reported he claims that Myers and Steadman suffered from Munchausen’s by proxy — a form of mental illness whose sufferers deliberately harm their children, or make out that they are unwell — and that they had been ‘regularly drugging’ the four children with substances similar to those that caused their deaths.

This comes after the Mechanicville Police Department confirmed that over-the-counter drugs diphenhydramine, the active ingredient in Benadryl, was ‘present at fatal or lethal levels in all six individuals’.

Meanwhile mitragynine, one of the primary compounds in Kratom, which is sold commonly over the counter at gas stations and convenience stores, was found in four of the victims.

While three of the children succumbed to fatal poisoning, 10-year-old Gavin had been stabbed, with injuries indicating he had tried to protect himself during the attack.

A handwritten confession signed by Steadman was found inside the property, Mechanicville police chief Bill Rabbitt confirmed.

Harmon originally raised the alarm after the children missed a scheduled video call with him on June 13, while a neighbour, Stephanie Sweeney, later requested a welfare check after saying she had not heard from them in days.

The six bodies were found just days before the children had been due to travel to Utah to spend the summer with Harmon, who had not seen the children in person since 2019, and who had been locked in a custody battle with Myers.

She had been due in court for a custody hearing on June 29 amid claims she had not been sticking to the parenting plan.

Myers claimed on social media that she was a victim of domestic violence — a claim Harmon stringently denies — and shared a GoFundMe created by a friend weeks before her death which said she needed to raise money to travel to Utah for a custody battle, and to find a lawyer.

Investigators later said of the note found at the scene: ‘The author accepts responsibility for what occurred and states that they believed killing the children was the only way to keep them safe from alleged abuse in Utah.’

They added: ‘The author also claimed that Sarah Myers had done everything she could and that no one would help her, and acknowledged that the events did not unfold as they planned.’

Investigators also recovered a series of handwritten papers that appeared to have been written by Sarah Myers.

Rabbitt said: ‘Although those writings were unsigned, the author repeatedly referred to “my babies”, expressed anger toward the Utah family court system, made allegations that she and the children had been abused while living in Utah, and complained that she had been unable to obtain legal representation.

‘Whatever [Myers and Steadman] believed justified their actions, the deliberate murder of four children cannot be described as protection.’

He added that police could not independently verify any allegations of abuse against Myers or her children.

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