Victor Owino, another childhood friend who was with Kimutai, explained that Kimutai had surrendered before the fatal shot.
"It was so fast. We heard gunshots, then we saw Brian lying down. We rushed to help him, but the police officer who shot him was coming toward us, so we ran for our lives. We are all sad. We just want justice for our brother," he said.
"I have not been able to sleep after seeing my friend in a pool of blood," Owino said.
Kimutai is among the 19 people killed by police officers during the countrywide Saba Saba protests on Monday, 7 July.
At his home, friends and family gathered to mourn. They have remained there since morning, consoling one another for the tragic loss of a young man whose life was cut short by those meant to protect him.
His mother claimed that the officer who killed her son is well known to the family and that they had an ongoing dispute over a motorbike.
Her son was shot just a few metres from their house, along Kitengela Prison Road.
"I was with Brian in the morning. He told me he was not ready to go out for the protests-he was neither a looter nor a protestor," she said.
According to witnesses, she added, the officers marched towards Kimutai. He knelt, raised his hands in surrender, but was sprayed with bullets by the same officer.
The family is now demanding justice, calling for accountability for the killing of their son.
Human rights activists have stepped in, urging an immediate investigation into the incident. They are calling for the arrest and interdiction of the officer involved, as well as a broader probe into the use of force during the peaceful protests.
Friends mourned Kimutai as a talented and hardworking painter.
"We were painters, that's what we do for upkeep. He was such a good person," said Owino.