A federal investigation has determined that an overstressed 40-ton beam fell during demolition of the Touhy Road overpass over I-90, causing the death of Vicente Santoyo, a 47-year-old Omega Demolition employee, an injuring three additional workers.

According to OSHA, Santoyo was standing in an aerial lift cutting steel bracing between two beams supporting the highway when one of the beams collapsed on him in April.