Three drivers lost their lives when a co-worker opened fire during a company meeting last Wednesday.
RELATED: All 3 San Francisco UPS shooting victims identified
Many people have left tributes for Mike Lefiti, Benson Louie, and Wayne Chan.
RELATED: Family mourns Hercules father killed in UPS shooting
The gunman also died after shooting himself.
Monday's service was planned for noon-outside the UPS building on San Bruno Avenue near 17th Street.
The group organizing it conducts prayer services for all murder victims in the city.
VIDEOS: ABC7 News team coverage of UPS shooting in SF
RELATED: Sources say UPS shooter was SF resident Jimmy Lam
RELATED: UPS teamster says SF shooter filed grievance with company before killing 3
Click here for more information about the shooting.