The spotter on his right totally dropped the ball. Wasn't even close to the bar. Both spotters should have recognized the need to spot. On the slow motion replay u can really see the bar just crushing his thoracic area. Had to have broken many ribs which undoubtedly caused lung trauma. Bleeding from that point. Just a guess.
Cause of death as stated by the video description- "He died after injuring his heart,diaphragm,broken ribs and torn abdominal cavity". A news article claimed the slip was caused by using an open grip, but it looked to me like he had his thumbs around the bar. Fuckin sad.