Abstract: At 9:00 a.m. on April 3, 2024, an employee working as a plant operator for building materials manufacturer was reinstalling mixer blades onto the shaft inside a Vince Hagan HM-10 Horizontal Concrete Mixer. The employee had been on a crew between January 2024 and April 2024 engaged in the shaft and blade replacement and repair project involving the portable concrete mixer. The mixer sits approximately 6-foot high on a steel trailer frame. The entire assembly is designed to be raised and inserted as a component into a batch plant. The shaft sits within the mixer drum, which is approximately 15-foot long and 8-foot wide. The internal configuration includes a shaft down the center equipped with 4 blades. The employee was working with a coworker reinstalling the fourth and final blade onto the shaft. Two of the blades were at an approximate 9 o'clock position. The third blade was at an approximate 4 o'clock position. Both the employee and the coworker were inside the mixer drum attempting to rotate the blades to position to facilitate the installation of the final blade. They had attempted to spin the assembly using their own body weight. The first and second blades were jammed. Residual aggregate concrete had lodged between the blade and the outer wall of the drum. They placed a handheld chain hoist onto the lip of the drum and wrapped it around the second blade. The employee applied tension to the hoist chain and the first and second blades broke free and spun approximately 180 degrees. This created an unbalanced top-heavy condition when placed under tension with the hoist. Upon breaking free, the two blades spun and came to rest at the bottom leaving the blades in a reversed position. The coworker was able to maintain his balance, but the employee was struck in the chest by a portion of the blade and was knocked to the bottom of the drum. The employee died from blunt force chest trauma.