It was an indeed Ukrainian SAM launched to intercept a Russian rocket and it killed 2 at a wheat storage (they were loading a truck tractor, no info were they Polish citizens).

No "town" but outside a small village (and largely ethnic Ukrainian and now also full of Ukrainians from Ukraine) and no "shells" too.

Previously lost missiles and drones from both sides also fell in Moldova and Romania, and even in Croatia (https://www.aerotime.aero/articles/30463-mystery-as-military-drone-crashes-croatia).

Faulty Russian SAM missiles also repeatedly hit Russia (Belgorod region), falling down immediately or shortly after being launched. Elsewhere, one even turned back and hit the launcher: https://twitter.com/Militarylandnet/status/1540237527793242113

During WWII, people were wounded and killed in the "Battle of Los Angeles" when the American AAA mass fired at a literal UFO and probably at nothing at all. In the air, and on the ground. During the attack on Pearl Harbor, most (or even all) of the American civilians who died were apparently killed by the American anti-aircraft fire. Great numbers of people fell victim during this war to friendly AA fire in general, also in the air of course. It's even possible British AAA killed more people trying to shoot down the V rockets than were actually killed by the rockets.

Various S-300 videos: https://www.reddit.com/r/CombatFootage/search?q=S-300&restrict_sr=on&include_over_18=on

Oh, and also an Ukrainian S-300 once shot down an airliner full of Jews back in 2000 or so. They fired it a training target but it hit a passenger.

(Then of course a panicked Iranian air defense shot down an Ukrainian passenger plane full of Iranians during the Trump crisis few years ago, responding to a non-existing American attack.)

And several years ago, a Syrian S-300 killed a planeload of Russian soldiers in a troop transport that they mistaken for an Israeli F-16.