Abstract: At 1:30 p.m. on December 28, 2020, Employees #1 and #2, day laborers employed by a painting and masonry contractor, were repairing a retaining wall at a job site. They were working on the base of the retaining wall in preparation for a concrete pour. The two employees had not been trained by the owner of the company on the hazards of working on a retaining wall, and the owner did not have knowledge or experience with retaining walls or excavations. Employees #1 and #2 were using a Bosch Electric Grinder (SN 021024766) and a Bosch Electric Drill Hammer 8" pick to dig and clear needed space for a new footing support on the left side of the wall. No support system was used to protect the employees during the excavation process, and no underpinning plan was used. Both the left and right sides of the wall had been undermined by run off rainfall and/or snowfall for several months including days prior to the incident. The retaining wall suddenly collapsed on the two employees. Employee #1 sustained blunt force crushing injuries and was killed. Employee #2 was hospitalized with critical injuries.