Why would they extradite that person? The murder took place in country A and the leader of country B got killed. That's a problem for the courts in country A.
Some countries have a legal proviso that can activate their court system for crimes that didn't happen within their jurisdiction. Some Syrian torturers that ended up fleeing Syria too found themselves in courtrooms in the EU. So if the perpetrator was able to kill leader of B in A but then fled the country, if B somehow got ahold of them, they could prosecute their leader's murder on their own turf. That's assuming they wouldn't just send a hit squad.
All the headlines would just say things along the lines of "B-born naturalized citizen of A killed B leader." I think it's similar to all the al qaeda or IS terrorists who often held passports of the countries they terrorized.
The relations between these countries would obviously be strained. But how strained would depend on more factors. Where did security break down, who fucked up, and how did everyone react to this assassination? If B was indeed Russia and the shooter was Russian-born, you can bet they will come up with a media narrative how the culprit was long sought for gulag internment for their wild ideas but managed to flee from the glorious motherland. And then duped the hapless people of A to give them citizenship, the stupid, naive fools! If only they had listened to us, who are always right, before! Then this tragedy could have been averted.
I kind of get it if she's around and cannot tell if your chat is work-related or not. You could be telling your colleagues to go cut the red wire but she knows it ought to be the blue wire. She could've jumped in at that point to correct you, had she understood. But the bomb went off already and everybody died. I'm exaggerating the stakes here obvs.
I would try to keep shit in English when she's within earshot. And if she sneaked up on you while you're practicing your Spanish, apologize, acknowledge her wishes, and tell her you were just talking about the weather or the game or whatever. She might just be nervous about you talking about her behind her back - while she's in the room. So put her mind at ease. Don't piss off the higher-ups unless you're willing to lose the job.