Winter conditions with unstable snow can run into July in the Alps around Zermatt.
Not certain it was an avalanche - all five were visible from the air (rescue helicopter). So they hadn’t been burried in snow and/or sleet, but of course they can have been pulled down from the peak.
According to Swiss news the authorities are uncertain how long they have been missing. The victims haven’t yet been identified.
Another accident further north (avalanche) caused on fatality. Not a good day in the Swiss Alps.