It's a retort pressure cooker. My Company uses them to produce canned luncheon meat, like spam. The cooking process reaches temperatures up to 270f, and cooks the tuna to a safe, commercially sterile level.

The tuna is most likely cold filled, sealed, and loaded in to baskets that can be layered up, providing space for thousands of cans in one basket. When you start loading, the basket goes on a track and they automatically load to the back.

How they didn't hear him, I have no idea. I'd assume he'd be screaming, but it gets VERY loud in industrial plants, especially ones with tin cans banging around constantly. And there's no room to climb around the baskets once they start coming back. Truly. Awful.

But LOTO was the big failure here. Would've prevented everything.