Residents of the Polish village of Przewodów said they heard a loud "whoosh" just before a missile killed two Polish citizens on Tuesday, according to CNN.
The two people killed were farmers in working in a field, said CNN's Matthew Chance, who spoke with village residents familiar with the pair.
Poland, a NATO member, has yet to say if it's determined where the missile was fired from, or why it fell on Przewodów.
However, the country is considering invoking Article 4 of the NATO military alliance treaty, said Polish government spokesperson Piotr Muller, per Reuters.
Article 4 allows any NATO member nation to consult the rest of the alliance on issues of territorial integrity, political independence, or national security.