That Kyiv shooter is a good illustration of what problems Russians tend to bring. Born in Moscow, strong ties to Russia. Lived in Bakhmut, awaiting Russian army, but didn't stay in Bakhmut when it arrived. Moved to Kyiv to await Russian army there instead.

Poisoned available to him social media with hatred towards Ukraine, Jews, and his wet dreams about ethnic cleansings. Ultimately, unhappy with Russian army advances, decided to kill those hated khokhols himself Granted, the last part is somewhat uncommon even for the likes of him

However, the general tendency of living in a country, while never learning the language and quietly (or not so quietly) hating both on the country housing him and its inhabitants, is well-documented Russian behaviour pattern. Because you see, he is from Moscow, where people live.

And he's not learning your bumpkin-speak, just so he can please some aboriginals. Whatever petty grievances a Russian has, would never have happened if he lived under Russia, but he doesn't want to go to Russia, he wants Russia to come to him. And when it does, he flees further.

Does it always end like this? Not exactly. A Russian isn't necessary a mass murderer. However, a Russian will bring as much of Russia as he can into his new home. Whining about "Great Russian Culture TM", musings about "It Not So Black And White", a bit of eavesdropping, perhaps.

A bit of stories of "Great Misunderstood Russia" to whomever listens. A bit of "This Is Russophobia And Discrimination!" whenever Russian information warfare is being countered. Cynicism masquerading as wisdom, smug superiority masquerading as expertise.

A willing vulnerability in your country's defence as long as there is Russia to exploit it.