The Finnish authorities know exactly who did it, but what are they going to do?

Sanction Russia? Fire a few missiles at Moscow? Write a sternly worded letter?

It's just added to the pile of "shit that Russia does without repercussions" which is opened when (not if) they actually cross the border to Finland and find out what happens when you fuck around with a country who's been preparing for Russian invasion for 100 years.