I think you did the right thing. In this case, the child was beyond the state of reasoning. No talking would have changed his behavior. Only the very real and immediate feeling of pain could suffice. Once calmed down, he would then realize the severity of his actions, put two and two together, and think twice before acting that way again. My .02.

When I was a child, I never acted out physcially against anyone. I did, however, have fits of rage ("temper tantrums") a lot, mostly due to frustration. My mom would send me to my room and if I didn't stop stomping and screaming there she would fill up a pot with cold water, open the door to my room, and throw it at me. Got my attention real quick and I'd shut up immediately.

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Current:
2014 VW Tiguan SEL 4Motion 43,000 miles.

2016 Hyundai Santa Fe Sport (wife's).

Past:
2006 Jetta TDI 135,970 miles. Sold Nov. '13.
1995 E-320 Special Edition. 220,200 miles. Sold Sept. '07.
1987 190-E 16 valve. 153,000 miles. Sold Feb. '06.
1980 300-D 225,000 miles. Donated to the National Kidney Foundation.
1980 240-D manual, 297,500 miles. Totaled by inattentive driver.