Some of my initial thoughts that came up about the Missile hit in #Poland based on limited information available right now.

Reactions to it are again emphasizing how people least in the know tend to overreact the most.
It's understandable, for it's not something laypeople have to ever even think about, but on the other hand nothing new or an unpredictable scenario for anyone who's versed in such matters or Russo-Ukrainian war in particular.
So far nothing unthinkable has happened for which wouldn't be prepared for. Scenarios like this are what militaries and other relevant institutions prepare for as their full time job.

Two likely scenarios involve a simple mistake with soviet/russian made missile systems, for which such an event is not particularly uncommon. Soviet made SAMs in particular tend to stray wildly when they do and Russian missile operations have not impressed with their precision or competence in this conflict. In other words an honest mistake is entirely plausible.

Third, but not necessarily least likely scenario is Russia intentionally testing the reaction for whatever it is planning. This again is also no panic time.

All three are quite easy to overlook politically and even if a reaction is demanded to the third, there's a range of relatively secure courses of action that can be taken in response that are strong, but not really changing anything major about the situation nor one's posture.