Eight-year-old terror victim Saffie Roussos called out for her mum as she was held by a first-aider in her dying moments.
Distraught Paul Reid, 43, tried to reassure the little girl that she would be OK as they waited for help amid the carnage in the Manchester Arena.
In an exclusive interview with The Sun, Mr Reid said he dashed back in to look for the terrorist after he heard the bomb at the end of the Ariana Grande gig on Monday night.
Instead he found himself comforting the injured strewn across the floor, including little Saffie, who he wrapped in his coat before helping onto a makeshift stretcher.
He discovered the following day that she had died in hospital from her devastating injuries - the youngest of the 22 killed in the atrocity.
Dad Paul had been at the concert and was one of the first to dial emergency services after hearing evil Salman Abedi blow himself up in the foyer.In floods of tears the forklift truck driver said yesterday: "She was a dying little girl and she just wanted her mum. It was devastating."
He recalled: "The concert was just about to end and I was at the bottom of the stairs at the main exit. Then I just heard a boom. I could see dust, smoke and stuff flying around.
"I ran back up the stairs and I was actually looking for a terrorist. I knew it had been a bomb.
Paul then wept as he described seeing a dying teenage girl just a few feet away.
He said: "She was trembling all over."
Paul then told how he saw Saffie, who had been at the concert with her mum Lisa and an older sister.
She was lying 15ft from an exit door wearing a T-shirt, leggings and ankle boots. He said: "I saw the little girl was conscious and I said, 'What's your name?'
"I thought she said Sophie. When I asked her how old she was she said she was eight.
"I wanted to keep her talking and asked her if she had enjoyed the concert but then I realised she was having difficulty breathing.
"She said, 'Where's my mum?' I said to her, 'I don't know but we are going to find her in a minute. Don't worry. We are going to sort it out. You are going to be all right'.
"The little girl's legs were mangled in a bad way and she had a big round hole above her hip but there was no blood coming out of it. She also had a big head injury to her temple.
She said, 'What's happened?' What could I say to her? I just tried to reassure her, then one of the paramedics came.
"She cut the girl's trousers off, did a quick assessment and told me to stop with her.
"The girl kept trying to fall asleep but I knew I had to keep her awake and conscious. I was stroking her face and saying, 'Come on Sophie stay awake. You're going to be all right.
They are coming to take you away in a minute.'
"But she kept drifting into unconsciousness. I cannot bear to think about it. Then she started shivering and told me she felt cold. I took my coat off and put it over her but she was still shaking a bit.
"Once we got outside one of the police flags down an ambulance. We gently put her in and she is still alive with her eyes open. That's the last time I saw her."
Paul rang the police when he arrived back at 4am. He recalled: "I asked the operator what happened to a little girl called Sophie but no one could tell me anything."
However, when he saw the news reports the next day he recognised one of the first victims as the girl he had tried to save.
Paul said: "I saw the pictures and knew it was the child I called Sophie. We did our best to save her but in the end no one could.
"I only knew her for a few minutes but I will never forget her."