Hello,
Why I did the pk: Rule 20 Mugging rules- "i.e. you may not perform vigilante justice and must have a group member connection or F3 of the person you are saving in order for the kill on the mugger to be considered a PK. While intervening, provided you are not being mugged or held under fear rp yourself, you are not at major risk of pk." Which case i interpreted part of the rule as not needing to have the F3 prior to the interaction as long as there was a group connection. (Colombo aiding a Kosher Ally).
Why I was wrong: They need to have the F3 prior to the mugging, he was not apart of the RP and inserted himself.
Mistakes happen!