Is hitting an 11‑year‑old with a belt out of anger considered abuse?

I just learned from my grandma that a couple weeks ago, my godson (11 year-old boy) has been having an attitude for a while. According to her, his mother (my aunt and mom's younger sister) couldn't take it anymore, he really pushed her button too much that she hit him 10 times with a belt, so hard that it left small purple bruises on his bottom.

Aren't you suppose to calm down first before making any decision? Anything done in anger and frustration is bad. This is what tends to happen when you lose your cool; you can overdo it and escalate. Lastly, she never took time to find out what exactly my son is upset about. He's been upset and having personal issues for a while. In addition, when he was younger he used to get yelled a lot whenever he couldn't get the right answers for his homework, leading him to having a stuttering issue and speech delay before.

Updates
4 mo
Instead of being concerned and finding out what problems her son is having, what issues (what if he's getting bullied too), she takes her anger on son like that.

Leaving bruises (regardless of whether you think the child deserves it or not) is abuse to me.
Is hitting an 11‑year‑old with a belt out of anger considered abuse?
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