Police have released surveillance video of one killer and sketches of the other two, hoping someone will turn them in. A $50,000 reward is being offered in the case.
Police said last September, one attacker arrived at the Joy & Louis corporation on 18th street to pick up a purchase.
When he walked out, two others forced their way in. A struggle ensued and one of the men stabbed 75-year-old Min Yin of Arcadia.
He remained in critical condition until his death nearly four months later.
Anyone with information is asked to call the Los Angeles Police Department at (877) 527-3247.