An employee was using a corded portable grinder to cut off the top of bolts around the trim of a tempered glass window frame/pressure plate in order to reseal a sloped tempered glass system. He was on a piece of foam on the glass panel. The grinder nicked the glass causing it to shatter. The employee fell through the glass to the floor 10 feet below sustaining cuts and punctures from the glass, and a brain bleed/concussion. The employee was hospitalized.