Learn Russian: Что здесь произошло?

The question word что (what) is the subject of this sentence. In Russian, when что is the subject, the past tense verb must always take the neuter singular ending -о.

Why use the perfective verb произошло rather than the imperfective происходило?

The perfective произошло focuses on a completed event and its result, asking what has already finished happening. If you used the imperfective происходило, it would mean "What was happening here?" which focuses on the ongoing background process in the past.

Could I use случилось instead of произошло here?

Yes, Что здесь случилось? is perfectly natural and means the same thing. Произошло is slightly more formal and often used for specific incidents or accidents, while случилось is very common in everyday speech for sudden or unexpected things.

How would I answer this question using the prepositions of cause from this lesson?

If the event was caused by an involuntary emotional or physical reaction, use от plus the Genitive case, like Это произошло от страха (It happened out of fear). If someone caused the event due to a conscious motive, use из plus the Genitive case, like Он сделал это из любопытства (He did it out of curiosity).