unknown boys, probably around 15 years of age, threw THIS BIG rocks at adult people who were at public sauna in Helsinki beach
iltalehti.fi
the sauna is in jätkäsaari, an island on the sea that connects to Helsinki with a 50 meter long bridge
the boys went to the island for some reason and had picked up coast rocks and then they threw rocks at adult people inside a sauna
then the boys ran away, crossing over the bridge and disappeared onto streets of Helsinki
you cant throw the stones at people who inside sauna itself because it is a closed construct but when people come out of sauna, they are vulnerable to hail of stones that come from the sky