A gamer????? really???? you mean ROP gamer?
Look up homicidal ideation. Video gamers can play out various fantasies, and for a person who has a homicidal ideation situation...games like World of Warcraft allow them to play out the idea. In this case, the guy likely went to the next step and wanted to kill a massive body count. He wasn’t functioning in the same world as you or I.
If you look at plain suicidal guys/gals....they tend not to involve others in their situation.
This guy was exceptionally different.
Around five years ago in Germany....we had a gal around Christmas who intently walked across the Autobahn near Ramstein and arranged for herself to get hit by a car with two AF folks. It wasn’t just a suicidal thing....she wanted involvement of others as well. Killed the nutcase in that case, and two AF folks survived but it was a hard experience on both.