They were a few brief minutes that Arash Hejazi will never forget, that have changed his life for ever, that have shocked the world and ripped every last shred of legitimacy from Iran’s tyrannical regime.

There was the pandemonium of the protests, the terror as the riot police charged, and the sudden crack. And there was this beautiful young woman looking down at her chest in surprise as the blood gushed out.

Dr Hejazi rushed to help as Neda Soltan’s life rapidly ebbed away. She could not speak, but he said: “I felt she was trying to ask a question. Why?”

Why? Why had a presidential election that generated so much excitement and exuberance ended with a government that claims to champion the highest moral values, the finest Islamic principles, butchering its own youth?

Dr Hejazi, 38, trained as a doctor, but later turned to his real passion — literature. He became a novelist and editorial director of a Tehran publishing house. He has spent the past seven months with his wife and infant son doing a postgraduate course in publishing at Oxford Brookes University. He was caught up in the excitement of Mir Hossein Mousavi’s campaign. He believed he could change Iran.On June 12 he went to London to vote, and encouraged all his friends to do likewise. The next day he flew back to Tehran on business and found a capital convulsed by running battles between the security forces and hundreds of thousands of Mousavi supporters who believed that President Ahmadinejad had stolen the election.

The following Saturday, shortly before 7pm, he was sitting in his office with three friends when they heard a commotion in nearby Kargar Street. They went to see what was happening and found riot police — some of them on motorcycles — charging towards a huge crowd of protesters, firing teargas and lashing out with their batons. It was terrifying, he said. Everybody started running. But amid the pandemonium he noticed Neda Soltan. She had been caught up in the swirling emotion of the moment. He saw her shouting “Death to the Dictator” and an older man pushing her — rather against her will — into a side alley, Khosravi Street.

Dr Hejazi and many others joined her there. They believed that they had found a refuge. Miss Soltan was standing just a metre away from him when “all of a sudden we heard a blast. I asked my friend what it was, and he said he’d heard the police were using plastic bullets. A second later I looked at Neda. She was just standing there, blood gushing out of her chest. She had bent her head to look at the wound, then put her hand to her chest. I just saw surprise on her face, then she lost control.”

Dr Hejazi and another man rushed to support her. They laid her on the ground. “I put pressure on the wound. From what I saw the bullet had hit her aorta and lungs. When the aorta is hit the blood drains from the body in less than a minute. There’s nothing you can do. She didn’t say a single word.”

He remembers the older man — later identified as her music teacher — wailing, “My child, my child”.

Miss Soltan’s body was bundled into a car, a Peugeot 206, which rushed her to hospital but it was pointless, Dr Hejazi said. She was already dead. “She died in my hands.”

As Miss Soltan was being taken to hospital another commotion erupted about 20 metres away. A crowd of demonstrators had caught the basij — an Islamic volunteer militaman — who shot her from his motorbike. He was a big, strong man in his forties, clean-shaven except for a moustache.

“I heard him shouting, ‘I didn’t want to kill her. I didn’t want to kill her. I meant to shoot her in the leg’.” The crowd were furious. Some were trying to lynch him. Others were saying: “We’re not killers. Don’t harm him.”

All agreed that there was no point in handing the man to the police so they simply took his identify card and let him go.

Dr Hejazi’s clothes were soaked in Miss Soltan’s blood. He returned to his office to wash. His friends joined him there and they sat for two hours, waiting for the streets to clear, discussing the horror of what they had seen. “I was pale and furious and afraid and sad,” he said. “As a doctor I’d seen death before, but I never thought I’d have such a feeling. It was not just her death, but the injustice of the thing and the gaze in her eyes as life was leaving her.” He did not weep then, but he did later that night in bed.

Dr Hejazi finally reached his parents’ home at about 10pm, which is when he realised that he was in grave danger himself. There on television — CNN or al-Jazeera — was the grainy footage, shot with a mobile telephone, of him trying to save Miss Soltan’s life. That 40-second clip was flashing around the world, making Miss Soltan an instant global symbol of the regime’s brutality. The authorities moved swiftly to silence her family, bury her body and prevent any wake. How long before they tracked him down?

Within a day or two friends were calling, asking if it was him in the video. He started growing a beard to disguise himself. He went to the office, but returned well before dark and avoided the demonstrations. He lived in increasing fear. “If I was identified I would have been arrested. I would have been one of the hundreds of people who have disappeared in the past ten days . . . Anything can happen in that country right now.”

He decided to return to Britain, not knowing if he would be stopped at the airport. He tried to conceal his fear from his parents, and on the telephone to his wife in Oxford, but on Tuesday he e-mailed his friend Paulo Coelho, the distinguished Brazilian novelist: “Trying to leave the country tomorrow morning. If I don’t arrive in London at 2pm something has happened to me . . . If something happens to me please take care of [my wife] and [son], they are there, alone, and have no one else in the world. Much love, it was an honor having you as a friend.”

Dr Hejazi made it. He flew out on the British Midlands flight on Wednesday morning and may never be able to return. He escaped, but he did not leave behind the horror he had seen.

Speaking from the safety of his Oxford home last night, he said of Miss Soltan’s death: “I can’t forget that scene. I live it every moment. I don’t know how I can cope with this. I don’t know if I can heal. I don’t sleep much now. I just fall asleep when I’m exhausted for a couple of hours.”

On his Facebook site he told his fellow students: “I’m not sure I can be your class clown any more. I have many scars now. Deeper than what I already had.”

He is outraged by the regime’s attempt to suggest that Miss Soltan was shot from behind by a fellow protesters — she was shot from the front, he insists. Or even more outrageously, as some Iranian government newspapers suggested yesterday, that the BBC’s newly expelled Tehran correspondent, Jon Leyne, arranged for her to be killed so he could get good propaganda pictures. “Oh my God. That’s outrageous . . . nonsense,” he said. Above all, he is consumed with fury at the rulers of his own country, who profess to rule in the name of Islam but slaughter their own people and violate its most sacred values. “It’s outrageous. It’s unbelievable. No government has the right to use such force against its own people.”

A coup détat has taken place, he said. “It may not sound like a coup because those who had power still have it, but it was a coup in the sense that the people chose someone else and they prevented him coming to power.”

His only consolation is that Miss Soltan has become a global symbol of innocence destroyed by evil. For that he is glad. “This way her blood is not wasted and she did not die in vain,” he said.

“She was everything that this movement is about. She was a civilian. She was against violence. She was not carrying a weapon. She was just shouting, just a person in the street who was against injustice going on in her country, and for that she was murdered.”