Why do some guys dig their nails in to my skin when shaking hands?

My mom was basically stalked by this African guy who when shook his hand dug his nails into her skin and she ripper her hand because it hurt. My sister went to Africa to find a man following her around and when they shook hands he dug his nails into her skin as well. Why do some people do this?Why do some guys dig their nails in to my skin when shaking hands?
i dont really know why you had to put the term 'African'; in here.


maybe its a cultural thing but i highly doubt it.

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