Translation in case you don't get the spelling:

What happened: "Jack showed me how to play Mercy"

Apparently this involves one kid bending the other kid's finger back as far as he can until the other kid cries "Mercy!"   (Sounds like a great idea!)  According to Alex, Jack went too far so he retaliated to the degree that they both ended up crying in the school counselor's office.

I felt:  "Mad"

The other person felt:  "Pain"  (Um, yeah, kind of to be expected)

Next time I could: "Not play rough games"  Well, at least not on the bus, pal.

This reminds me of a similar game my sister Alice and I played when we were little, which involved poking your fork into your sister's arm until she said stop (not in front of Mom, needless to say).  At two-and-a-half years older than me Alice was so big and super tough that she didn't stop me until 4 bright red pinpricks of blood appeared.  At which point she screamed bloody murder and ran to tell our mom that I had simply lunged across the table unprovoked and stabbed her in the arm with my fork.  Ahh, one of the many injustices inflicted upon us by siblings!  At least we were smart enough not to do it at school :)