He's referring to the Korean population in Los Angeles who took up rifles and went onto the rooftops of their businesses to defend against the looting, rioting, and murdering mob. This happened during the L.A. riots, 30 years ago.
Korean shop keepers that had to defend their shops with guns during the LA riots.
because LAPD is famously corrupt and racist. They took an equal opportunity stance during the Rodney King riots; they couldn't beat up the Koreans so LAPD decided to go MIA and not defend taxpayers' property.