Iraq and Afghanistan veteran Kevin Holt, 30, also blamed himself for the death of a three-year-old hanged by an Iraqi mob after he gave her water in a separate incident and fought a long battle with post traumatic stress disorder.
Now his story along with other service personnel who took their own lives is being told in the BBC3 documentary.
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The programme reveals how he never recovered from seeing his friends killed in an explosion or the death of the girl he had given water to.
PTSD – The War in My Head, highlights three tragic stories that ended in the death or suicide of young veterans.
Kevin was found dead in his caravan home in Thorne last summer after taking an overdose of morphine.
The programme reveals how when Kevin returned to the Iraq town after his tour months later, he was horrified to find out the tot had been hanged by a mob who were angry that she had accepted a gift from a British soldier.
Figures reveal that 17 per cent of those who served in Iraq and Afghanistan suffering from PTSD, and in 2018, it was reported that 71 army personnel or veterans had taken their own lives.
Kevin’s sister Jess Holt said: “Kevin always blamed himself for that (girl’s death). It really got to him.”
The subsequent death of five army colleagues on a patrol in the Afghanistan further compounded his struggles and Kevin was a changed man when he came home.
“I lost my brother when he went to Iraq,” she says. "As much as I loved him and he was my big brother, he never really came home.”
An only boy with four sisters, he always wanted to join the army and as a youngster would build forts in the garden and spend hours playing with plastic toy soldiers.
At 18, he signed up and was quickly deployed to Basra, where the incident with the little girl occurred.
When he came home he began suffer mood swings and anger issues.
In footage filmed for another documentary in 2012, he said: "At one point I smashed up my room, smashed my TV up and everything and I don’t even know why.”
In 2007, he was diagnosed with PTSD and was given mental health treatment by the army, including a period in hospital.
But he convinced medics he was fit enough to return to the front line, saying he wanted to “soldier on”, and in 2009 he was sent to Afghanistan.
On July 10, his company went out to sweep for IEDs – Improvised Explosive Devices. Kevin was operating the metal detector used to find them when a series of devices exploded.
The blasts killed five colleagues, including best friend James Backhouse.
“For him it wasn't the initial explosion that got to him,” says Jess. “It was afterwards picking all the bodies up. It's the stuff of nightmares.
“He was an over thinker and he couldn't shut it off, his head just couldn't move on from that day really.”
Despite an award for bravery and an MOD ruling that he was without fault, his army dreams were over.
After returning home, Kevin struggled to hold down a job or find a relationship, because of his PTSD, which left him paranoid and prone to violent outbursts.
He later said: “When I got out the army, that’s when the help stopped. I was just going down from there.”
Worried about him mum Shirley got him a dog, Dash, who was trained by a veteran charity tom help with symptoms of PTSD, waking him when he nightmares and calming him down when he was angry.
But two years ago he was diagnosed with testicular cancer and he moved into a caravan next door to his mum’s.
“He still had paranoia and phases where he wanted to be on his own and shut the world out,” says Shirley. “But focusing on getting himself better from the cancer distracted him a little bit.”
The coroner ruled his death in July 2018 was by misadventure and said Kevin accidentally overdosed on the morphine he’d been prescribed for his cancer.
PTSD - The War In My Head is available now on BBC3