You would instead say: "Què ha estat/sigut això?".
The simple past (fou) and the periphrastic past (va ser) are equivalent, the difference is only the dialect and register. The simple past is only used in daily speech in Valencia and its surroundings, elsewhere it's just literary. Anyway those wouldn't be used here because you can't use them for actions which happened today, you need the present perfect. In the same vein:
Dymn is right although, in the second example, using què va passar? would be correct in case we were referring to something that happened at a particular moment in the past that we already know about. For instance:
- Ahir al vespre el Joan i el Pere van coincidir al mateix esdeveniment.(Yesterday evening John and Peter happened to meet at the same event.)
- I què va passar? Van arribar a les mans?(And what happened? Did they "get to their hands" = end up fighting?)
> In the mind of the speaker, this what happened refers to "at that finished event", not to an undefined time or a reference of time in which we're still at. In these latter cases, què ha passat is used.