I expected “sie” not “die” here. Does this mean there’s a specific group of people previously mentioned, which “die” refers to?
The usage here is like a hybrid between a definite article and a pronoun. Imagine that there’s a plural noun after it that has been dropped, because they have just been talked about:
- Vorhin haben Spaziergänger eine Leiche im Wald gefunden.
- Haben die (Spaziergänger) es schon der Polizei gemeldet?
Although “sie” would also work. But it can be mistaken for the formal you (in speech).