It's like watching dominoes. You hit one and the rest fall down.
This guy looked to be squeezing by some pallets in the middle of the aisle when he barely touched the shelves. That set off a domino effect knocking everything down. The man got buried under whatever is on the shelves.
I would say it's all the guys fault, however, it looks like he barely touches the shelves. Almost like too much was placed on them to begin with.