Three US officials have said that the missile that hit Poland was fired by Ukraine, as we read in the Daily Beast:

Seemingly confirming Biden’s suspicions, three U.S. officials speaking to the AP on the condition of anonymity suggested it was Ukraine that fired the missile, citing assessments that indicated the missile was fired by “Ukrainian forces at an incoming Russian one amid the crushing salvo against Ukraine’s electrical infrastructure Tuesday.” The Polish Foreign Ministry had earlier said the missile in question was “Russian-made” but stopped short of blaming the strike directly on Putin’s troops. Russia, for its part, has denied it had any hand in the attack, which killed at least two people near Poland’s border with Ukraine.

When this situation was first being discussed, General Patrick Ryder said that the Pentagon could not confirm if the reports of Russian missiles hitting Poland are true:

“We are aware of the press reports alleging that two Russian missiles have struck a location inside Poland near the Ukraine border. I can tell you that we don’t have any information at this time to corroborate those reports and are looking into this further”

But this did not stop people from emphatically declaring that it was Russia who struck Poland.