Last week, a convoy of buses carrying evacuees from nearby villages stopped briefly in rebel-held Rashidin, west of Aleppo. The Telegraph quotes local reports saying a man lured children waiting near the buses over to a car with packets of chips. Then, a bomb was detonated. The attack claimed 126 lives, killing more than 80 children.
Photographer and activist Abd Alkader Habak, who was working nearby, was briefly knocked unconscious by the powerful blast.
"The scene was horrible - especially seeing children wailing and dying in front of you," Mr Habak told CNN. "So I decided along with my colleagues that we'd put our cameras aside and start rescuing injured people."
The first child he checked on was dead, Mr Habak recalled in horror. Then he ran towards another. The boy was barely breathing. He picked him up and ran towards an ambulance.
"This child was firmly holding my hand and looking at me," he said.
These haunting photographs were taken by Muhammad Alrageb, another photographer at the scene.
Mr Algareb told CNN he also helped some of the injured civilians but then began taking photos.
Mr Habak said he did not know whether the injured boy survived. He left in the child - who he guessed was around 7-years-old - in an ambulance and rushed back to the scene of the bombing.
That's when the photographer came across another child on the ground.
This devastating photograph, shot by a different photographer, shows Mr Habak on his knees wailing near the boy's body.
"I was overcome with emotion," he told CNN. "What I and my colleagues witnessed is indescribable."
Pictures of Mr Habak have been shared tens of thousands times on social media.
What I and my colleagues have done today is what inspires our humanity to those who were partners in killing the children of #Khan_Sheikhan— Abd Alkader Habak (@AbdHabak) April 15, 2017
And people are moved by the haunting images.
@AbdHabak Your actions yesterday were truly heroic. In the chaos your very first instinct was to help. You are incredibly strong and inspiring.— Jennifer (@JennRollins1002) April 16, 2017
@AbdHabak You and your colleagues show us that good is still alive in this awful world. You are heroes. May God keep you all safe, give you strength.— Bint Abu Banned (@itsmenanice) April 16, 2017
@AbdHabak I don't know you, we will probably never meet but what you have done today made me proud of being human. thank you.— Francois Randazzo (@F_Randazzo) April 16, 2017
Syria's war has left more than 320,000 people dead since erupting in 2011.
Click here for more trending stories.