His mother, Gillian Munyao, told reporters that her son had joined the protest after work and that he was shot in the city center while dodging tear gas.
“The only mistake Rex made was standing up for everyone’s rights,” Munyao said, adding, “We want justice for our child.”
His father, Crispin Odawa, said he was “a very quiet, peaceful and obedient child.”
Mr Masai was taken to Bliss Hospital on Moi Avenue in Nairobi, where he was pronounced dead.
“He was shot in the upper mid thigh. He appears to have bled to death before being transported to our facility.” one doctor told Kenya's Nation news website.
Kenyans took to social media to mourn the young man and demand justice.
“We will print posters around Nairobi with Rex’s face and name and call him a hero,” Hanifa Farsafi, one of the protest organizers, posted on X., OutOld Twitter.
“My heart is really broken, but it wasn’t in vain,” she added.
The Independent Police Oversight Authority (IPOA) said it had launched an investigation into the shooting., Out.
The opposition coalition, Azimio la Umoja One Kenya, called the shooting a “tragic incident with far-reaching consequences” and called for the resignation of police chief Japhet Kume., Out.
A total of 39 people were injured in Thursday's protests, eight of whom were in critical condition, the Kenya Red Cross said.
Those with the most serious injuries were taken to Kenyatta National Hospital, Kenya's largest referral hospital, for further treatment.
A police officer lost both arms on Tuesday, Out After tear gas exploded before he could be thrown.
He was one of hundreds of police officers deployed to quell protests in Nairobi.
Amnesty International claimed that some police used firearms., Out It said more than 100 people had been arrested on Thursday.
The human rights group said, “Used cartridges were confirmed through real-time filming.”
It added that the victims suffered injuries ranging from “soft tissue injuries and tear gas inhalation.”
Law Society of Kenya (LSK) president Faith Odhiambo condemned police “brutality” and “illegal” arrests of protesters.
Police have not yet commented on the charges.
However, in the previous statement, OutThe police chief said protesters would not be allowed to access critical government infrastructure or disrupt congressional proceedings.
Despite the protests, the controversial bill was passed by a majority of lawmakers on its second reading on Thursday.
The committee will now move on to the next stage of considering the amendments, with a final vote expected next Tuesday.
Protesters want lawmakers to reject the bill in its entirety.
The government has often defended tax measures as necessary to reduce the national debt, which stands at about $80 billion (£63 billion).
