Abstract: At approximately 7:30 a.m. on February 20, 2015, three iron workers were erecting a steel stairway on a multi-story apartment and retail building. The stairway was being erected inside a shaft that consisted of masonry walls on three sides. The iron workers had rigged a horizontal wire rope between to the east and west walls of the shaft near the top of the shaft on the 3rd floor. A ? ton Harrington Chain Hoist (Model CF4) was supported by the horizontal wire rope and the hoist was used to lift the steel staircase members that weighed between 28-and-123 pounds. The first two levels of the stairway were placed with this system on February 16 & 17, and work did not continue on February 18 & 19 due to extreme winter conditions. On the morning of February 20, the temperature was approximately 8 degrees Fahrenheit, with wind speeds of approximately 7 mph and max gusts of approximately 28 mph. The three iron workers were working from the first floor of the stairwell and were attempting to lift a stair stringer and then lower it for stairway access to the basement. The west section of the 3rd floor masonry wall that was supporting the horizontal wire rope collapsed into the stairwell. Iron worker #1 was welding from an 8 foot tall Werner step ladder that was on the first floor, leaning against the east wall. The collapsing section of wall that was approximately 11 blocks high and 7.5 blocks wide, struck iron worker #1 causing fatal injuries. The masonry walls had been erected for the first 3 floors a couple weeks prior to the accident, but the masonry walls were not complete and were planned to be extended for the remaining floors in the future. The masonry walls had also not been filled with grout nor had the permanent rebar been installed. The masonry wall was attached to the wood structure of the building, but the top portion was greater than 8 feet tall and was not braced to prevent overturning or collapse. A determination was not made to assure that the masonry walls could adequately support the rigging method used for the stairway. Iron worker #1 received crushing injuries to the head, spine, back, and ribs area, and was killed.