Mandy Seamark, whose husband Gary Dunmore, 57, was murdered in 2023 in a brutal double slaying speaks for the first time since the tragedy during tonight’s episode of 24 Hours in Police Custody: A Family Vendetta on Channel 4
The mum of a man “executed” in a double murder after a custody battle involving their grandson said the “callous” killer was motivated by jealousy.
Stephen Alderton, 67, blasted his daughter Samantha’s ex-partner Josh Dunmore, 32, and his 57-year-old dad Gary with a Beretta shotgun after a family court hearing.
Speaking during tonight’s episode of Channel4’s 24 Hours in Police Custody: A Family Vendetta, Mandy Seamark, Josh’s mum, breaks down as she says: “[Alderton] shot Gary for himself because Gary was everything he wasn’t.” Speaking for the first time since the rampage, she adds: “As a mother, your role is to protect your children.
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“It’s very difficult, you go all through your life, with your family values, everything about what’s right and what’s wrong, for [Alderton] to then do that to my child. He’s my child, mine. You’re there to protect them and he just callously just did that.” Alderton’s two victims were found dead in March 2023 at their homes – six miles apart in Cambridgeshire – just two days after a family court hearing over his seven-year-old grandson.
Following his arrest Alderton told police: “Sometimes you have to do what you have to do, even if it’s wrong in the eyes of the law.” The ex-chartered surveyor, who admitted double murder, was jailed for life at Cambridge crown court and must serve a minimum 25 years, later increased to 30 years.
After being arrested he initially refused to answer questions and only showed a shred of emotion when quizzed about his grandson. When asked by the custody sergeant how he was feeling as he was booked in, Alderton replied: “It’s not exactly the best day.”
During his interview, a detective asked Alderton: “How do you think your grandson is going to feel about the death of his father and his other grandad? Talk to me about your grandson, are you close?” Alderton replies: “Yes.” The detective says: “He’s lost his dad, he’s lost his paternal grandfather, and it’s looking like he’s not going to see his maternal grandfather for quite some time.”
Seeming to breakdown, Alderton says: “No comment.” Later he told the Channel 4 cameras: “Down in Texas, they have a particular approach that you have to respect because ion red-kneck country they have guns and things like that.” After his arrest, he was also recorded saying: “I come from a world where you look after your family.”
Alderton’s rampage on March 29 2023 came two days after a family court hearing involving his grandson, who cannot be named. Josh had stopped his ex – Alderton’s daughter – Samantha Stephen, and her US airman husband, Paul, taking the seven-year-old to live in America.
Alderton shot Josh twice in the hallway of his home in Bluntisham, Cambs, at 9.09pm. Thirty-one minutes later, he shot Gary three times in the hallway of his Sutton home, six miles away. The killer fled in his motorhome but was arrested the following day on the M5 near Worcester.
Before the killing, he wrote a series of text messages saying he would “override any court decision” and that there was “always a plan B” following the custody row. Judge Mark Bishop said the killings amounted to “an execution”.
The second episode of 24 Hours in Police Custody: A Family Vendetta airs tonight on Channel 4.
