This is the 4045th most frequent Polish word.
zastal
The Polish word "zastał" means "he found" or "he came across" in English, referring to encountering something in a certain state.
In this sentence, 'zastal' is used to indicate the rain coming upon us unexpectedly, thereby 'catching' us in a situation.
Zastal nas deszcz, gdy wychodziliśmy z domu.
Rain caught us as we were leaving the house.
Here, 'zastal' is applied to signify that upon his return, he encountered or found the changes that had occurred.
Zastal wiele zmian w firmie, gdy wrócił z urlopu.
He found many changes in the company when he returned from vacation.
In this example, 'zastali', the plural form, indicates their discovery or observation of the state of the house upon arriving.