Names are Russian in origin, but there are several reasons why they could be:
1) people who arrived during Soviet times, like Maksims Sirokovs (Maxim Shirokov) parents, who are Russians but you cannot tell by him because he went to Latvian school
2) ''old'' Russians who have lived here for generations, maybe some have already assimilated and only the surname shows that it is Russian in origin
3) given surnames to local peasants... like with Andersons and and other ''sons'' the guys are not Scandinavian, but it's a relic of Swedish times in Latvian when locals were given Swedish surnames, the same with Rēdlihs and other German sounding ones... with Russians it was not as common, as Russian Empire came here already later and there was not much of Russian landed nobility here anyway, but still- some could be named in Russian surnames, some could have changed them to be more ''Russian'' when at that time it was useful.
Like ''Masaļskis'', the surname sounds like a Polish one/Slavic, but I wonder if he has had any Polish relatives at all.