Footage of the July 2015 party, shot by activist group Aleppo Media Center, shows a costumed and face-painted Anas al-Basha at the center of the festivities, bouncing a smiling girl on his hip as music plays and youngsters clap along with the tune.
Clown and entertainer Al-Basha, 24, was killed Tuesday in a missile strike in the Mashhad neighborhood of the city's rebel-held east, his brother Mahmoud Al-Basha told CNN.
Al-Basha was a director at Space for Hope, a local non-profit that has worked to provide civil services to people living in the war-torn opposition area.
Zein al-Malazi, al-Basha's colleague at Space for Hope, shared video clips with CNN showing his friend distributing gifts to children in October 2015.
"We've tried to give out candy to the kids in liberated parts of Aleppo to bring them happiness and smiles to their faces, in spite of the airstrikes and destruction they're being exposed to," al-Basha explains in the footage, which shows children following him down the street as he hands out presents and candies.
Al-Malazi shared a post on Facebook about al-Basha on Thursday, writing, "To the soul of our beloved friend: Anas al-Basha ... you will stay in our hearts."
Other Aleppo activists shared similar messages on Facebook marking Anas's death.
"No one that knew him didn't like him," Monther Etaky, who said he volunteered with al-Basha at various NGOs in the city, told CNN. "He was so kind."
Life under siege
Mahmoud said his brother had refused to leave Aleppo, deciding instead to stay and help bring happiness to children in the city.
"He wanted to stay to continue his work, to help the children and orphans in Aleppo," Mahmoud told CNN in a phone interview. "This year they started to create schools underground, they would do activities for the children in basements and safe spaces. Before they used to go to gardens and be in the streets."
UNICEF estimates that some 100,000 children are living under siege in eastern Aleppo alone. According to the intergovernmental organization, volunteers in besieged areas have built underground play areas and schools for children hoping to continue playing and learning amid airstrikes.
Mahmoud last heard from his brother three days ago, just before he was killed. Anas sent him an audio message on instant messaging service WhatsApp, saying how crazy the situation was in Aleppo. Mahmoud says he could hear the rumble of jets and the sound of an explosion in the background.
"All I could say was good luck," Mahmoud said.
Anas was studying history at Aleppo University when anti-government protests broke out in Syria more than five years ago, sparking the civil war. He left school and began working with NGOs in opposition-held areas.
In his post on Facebook, Mahmoud wrote: "Anas is not a terrorist!"
"I wrote that because the Russians and Assad regime are saying every day that they're targeting terrorists in Aleppo," Mahmoud told CNN. "Who is dying every day in Syria? Civilians, children, women, people like Anas."