Warning: This video contains images which may disturb some people.
At least 68 children are among those killed in a suicide bomb attack in northern Syria on Sunday (local time).
The explosion killed about 120 people waiting to be evacuated to safety.
The convoy came under attack as refugees from government-supporting towns waited in a rebel-held area on the outskirts of Aleppo.
No one has claimed responsibility for the explosion. Syrian state media blames a suicide car bomber, and rebel fighters say Bashar al-Assad is responsible.
Activist and cameraman Abd Alkader Habak was not far from the convoy when the bomb went off and says "words cannot describe what happened".
"I was standing next to a car distributing food to the children. I was just a few meters away, when suddenly there was a massive explosion. My camera fell to the ground and I was thrown backwards," he said.
"I got up to see what was going on. I searched for my camera and found it there on the ground and saw a child lying there. He was bleeding.
"So I ran towards him. I looked at him and he was moving his hand. I looked at his face and I could see he is breathing. I picked him up and started to run towards the ambulance. I don't know what happened to the child, but I put him in an ambulance and they took him to one of the hospitals inside the rebel-controlled area."
Since the bombing, more civilians have been evacuated from towns besieged by both sides - saving lives, but dividing an already bitterly divided country still further.
Channel 4 News