Under the hood spoilers! - Nf jryy nf gur 'snpgvbaf' V'ir ersreraprq jurer fbzr Ryrpgbef nccebir be qvfnccebir bs pregnva trareny npgvbaf, rirel Ryrpgbe nyfb unf n onfvp nyyrtvnapr gb bar bs gur sbhe Vzcrevny enprf, naq gurer ner gvzrf jura lbhe npgvbaf znl gevttre nccebiny rssrpgf sebz rirelbar jubfr yblnygvrf yvr jvgu bar tebhc be nabgure. Fb lrnu, vs fbzrbar jvgu Zlexxna yblnygvrf jnf evtug ba gur phfc bs jnagvat lbh qrnq, gung pbhyq unccra.
Now technically it doesn't *quite* make sense for it to change based on that event because normally you would need to hire an assassin ahead of time, but OTOH it's kind of funny so I don't feel a big need to write around it, unless it really bothers people. It's kind of fun having the option of such an easily-changeable trigger.
I don't remember exactly what patch that particular assassination possibility was added in but it wasn't in the first beta releases so yeah if you haven't played for a while it could be a surprise.