Should I be worried about my grandpa abusing my grandma?

My grandma is 83, and my grandpa is 78 if that really matters. My grandpa had lost his temper and harmed people before, but he's never done it around me. Anyways, a long time ago my dad, and my grandpa and cousin were fishing in a boat. My cousin did something stupid I guess and then threw my cousin across the boat. I was just talking to my mom about a man I saw at the store slap his sons hand because he was reaching for a candy bar. I asked my mom if she thought that was wrong, then she went on to say that when she was a girl, my grandma told her to empty the dishwasher. My mom wouldn't do it, so my grandpa pulled my mom by the hair I guess. I'm slightly worried that my grandpa loses his temper like that on my grandma. There are really no signs, and I asked my mom if my grandpa has ever harmed My grandma and she said no, but I'm still worried. Should I be worried? What should I do?

Should I be worried about my grandpa abusing my grandma?
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