Guy was bitten by a spider called Brown recluse spider (Loxosceles reclusa, Sicariidae) on the thigh. This species lives mainly in the USA, but also in parts of South America. Although not lethal, its venom contains enzymes that can lead to serious complications. They cause tissue necrosis. That’s exactly the case with the man in the photos. He suffered extensive necrosis that had to be surgically removed or risk blood poisoning.
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https://en.wikipedia.org/wiki/Brown_recluse_spider