The shooter’s surname is Cruz. That is not a Russian name.
As far as the two boys’ first names go, Zachary is not a Russian name, and “Nikolas” is the Greek form of that particular name. The Russian form, pronounce in English would be Nikolia or Nikolai (also sometimes spelled with a “c” instead of a “k” when Americanized).
Adopted parents— Cuban American. Cruz. OK, know that.
Nikolai as a russian name often anglicized intentionally at time of legalization/adoption.
Not any “formal” anglicization method, and have several families am aware of where Kazahkstanis (and askenazi, oddly enough) had some “re-naming” of adoptees. My question would be one only available to the adoption documents.
In recent years/generations there have been many children of former Cuban/Russian parents (from the days of soviet/cuban, “cooperation”) who have matriculated in some fashion into the US. Their names are all over South Florida and NYC/Jersey. Here’s a “sample” kind of name, naturalized or not— “Mirta Nicoloff”.. (female, married to a real Russian, who married in Cuba, no kidding).