I haven't heard one media outlet claiming e.g. Dylann Roof was influenced by video games, and I think they would have a stronger case nowadays with games like Hatred on the market.
What do you mean by "nowadays with games like Hatred on the market"?
What is special about Hatred? It wasn't a particularly violent game, it just got propelled into notoriety by demagoguery and the developers' guerrilla marketing. It's a near verbatim clone of Postal, and that came out in 1997.