Didar Hossain was working in a garment factory opposite the Rana Plaza on the outskirts of Bangladesh's capital Dhaka when it collapsed last week, killing hundreds of people. Despite the risks, Mr Hossain went into the ruined building repeatedly, freeing those trapped. He told his story to the BBC World Service.
There was a sound, a really loud sound, and I realised something was wrong. I went to the window to see what had happened and the building wasn't there.
All I could see from the window was this dust-like fog - it was really dark, and smoky. We were screaming and trying to get out, but the security guard stopped us and said: "No, you can't go outside." But I pushed past him and went out.
We knew people were working in the factories and realised straight away that there would probably be a lot of people trapped in the rubble.
As a human being, I felt it was my duty to try and help other human beings. When I first went in I saw a dead body and I was frightened. But I gathered up my courage as I went on.
The building was nine storeys high, but it had become almost like a three-storey building. The upper floors had completely fallen down. I managed to get in through the sixth floor. When I first entered there was a body without a head - so I brought that body out.
The space was so narrow it was hard to get in. I put my head in as far as I could and realised I could break things and force my way through. I had a hammer and sometimes I got stuck, but I just carried on. I found that I could slide inside the tiles fitted there.
I was very frightened, obviously. It was dangerous, but if I had thought about it I would never have been able to save those people.
I saw that there were people still alive who were stuck inside, and that we needed to make some space to get them out. So I came outside to ask for equipment to help me slide them out. There were two other people with me - one was a driver, the other was a student from Jahangirnagar University.
I helped 34 people in total. There were two people who took a long time. One was a girl. I found her on the second day, and I spent five hours with her. She was 18-22m (59-72ft) inside, on the 3rd floor. She was alive, but her right hand was trapped.
She was crying a lot, and when I got to her she was saying: "Please brother, don't leave me, get me out - even if you have to cut off my hand." So I went out again and told a doctor who was there that he needed to cut off her hand to get her out. But he said: "I can't go in there, I'm frightened. You do it." So he gave me a knife and some anaesthetic so I could amputate her hand.
At that moment I was not frightened because I needed to save the girl. I knew that if I was afraid she would die. I did not want to cut off her hand, and I tried to save her without losing her hand.
I told her: "I'm leaving, you stay here and somebody else will rescue you". But she said: "No, please save my life, even if you have to amputate my hand." There was no other way, so with her permission I did it.
The anaesthesia was only in her hand, so she was conscious and could talk. She watched while I amputated her hand. She was screaming and I was screaming too, and I cried when I saw her crying. I felt really bad, but there was no other way.
After the amputation I tied her arm to her body, and then I tied her between my legs and tried to crawl out. I shifted slowly and brought her with me - that is how we got out.
[Next to the girl there were two men who were also trapped.] While I was rescuing her [one] man said: "Please rescue me or I'll die." He was stuck under a beam, and I didn't know what to do, but the man was saying: "Cut my leg off, but please save me."
I did not need much persuading - I used the knife to cut off his leg. He was very brave - he had no anaesthesia, and crawled himself to get out.
[The other man's] right foot was stuck under a beam, and I realised if I tried to break the beam it might collapse on us. So, he said: "OK, you can amputate my foot. I don't care because life is more than that".
I started cutting his leg, but he was screaming so loud I thought he was dying. But he was alive, so I tied his hands to mine and pulled him out.
I have been in touch with the girl, because it took five hours to rescue her, so we did have a chance to talk and I found out where she lived. The girl is now in intensive care in hospital, and she is in a better condition now. She is in a little pain, but she is OK.
I went to visit her at the hospital. She was looking at me before I even reached her bed. I asked her whether she recognised me and she said that she did and that I was the person who saved her life.
I wished her to get better and apologised to her - I explained that I did not have any other option than to cut her her hand. She said: "If you hadn't done it I wouldn't have got out alive; it's I who should say sorry to you for the hardship you went through in order to rescue me." Her parents had tears in their eyes and thanked me for saving their daughter's life.
I went in on Wednesday about 09:00; didn't [finish] until Friday at 13:00. I worked all that time. Whenever I came out I drank water and I always kept a bottle with me. There was always food outside the building, so I ate that and drank some water and then I carried on.
Afterwards I was ill for a couple of days - I couldn't eat anything, and had vocal problems. My family told me to rest, or go to the doctor, but I said I just needed sleep. But I couldn't sleep, not for days. Whenever I started to fall asleep I felt like someone was calling me.
I have a lot of memories, particularly about the hand and foot being amputated. And the dead bodies - they haunt me. Some had no heads; with one the eyes had come out. Those images are horrible and they still haunt me.
I never thought I was a hero - I'm just an ordinary person trying to help and I'm grateful to God that I could help.
- Didar Hossain was interviewed on Outlook on the BBC World Service. Listen via BBC iPlayer Radio or download the podcast.
- To celebrate Outlook's 50th birthday the team have brought together the stories of some of the most inspirational people they have interviewed - and they want you to suggest a person who's inspired you. Look at their website for details of how to make a nomination. The closing date is 1 May 2016.