At the American Legion Post 328 in Norco, mourners showed up in the morning to support Nikoui's family.
"Everybody wants to do everything and anything they can do to help. We're a small community and everybody knows everybody," said Natalie George with the Norco American Legion.
In honor of Nikoui, the community gathered for a pancake breakfast, followed by a hike to Pumpkin Rock where people came with flags, Norco High School colors and heavy hearts for their hometown hero.
Nikoui's former high school teachers remember him as a good natured student with a singular goal.
"All he wanted to do was go into the service and be a Marine. That's all he wanted to do... He just really wanted to be a Marine," said Ret. Sgt. David Spratley, an ROTC instructor at Norco High.
Social studies teacher Diana Stiller said videos showing him helping families and children in Afghanistan was "totally Kareem."
At the top of the hill, a former ROTC cadet and friend of Nikoui played Taps for all the fallen.
A ceremony in the evening also honored Nikoui. A procession of golf carts, trucks and horses paraded down a local street as people waved American flags in tribute to Nikoui.
Nikoui, 20, was among the three Inland Empire Marines killed in the attack. Hunter Lopez, 22, of La Quinta, and Dylan Merola, 20, of Rancho Cucamonga, also died.
Marine Staff Sgt. Darin Taylor Hoover, 31, who lived in Aliso Viejo, was also killed in the bombing. He had served in the Marines for 11 years.
Marine from Aliso Viejo among service members killed in Kabul attack
Several funds have been started to help the families of the Marines.
The family of Hunter Lopez requests that any who wish to make donations to honor his memory contribute to the Riverside County Deputy Sheriff Relief Foundation.
GoFundMe pages have been created in honor of Hoover, Merola, and Nikoui.