No I'm not saying that it was a movie or game that made him snap at all. I'm saying that he already had the fantasy but seeing something in a movie enhanced it. Like if he said to himself "Oh yeah, I like that, and he then incorporated that into his fantasy.
If a person is going to kill or has the desire to kill and everything about the crime scene in this case tells me he had that desire, then NO MOVIE will make anyone kill. It just helps their fantasy along, adds more detail to their already thinking. That is all I meant.
You're right, he probably did get some ideas from whatever he was watching or playing over the years. Media tends to be a lot more graphic today then it was 50 years ago. Things have moved on over the years, social norms have changed, expectations are different. It is interesting to compare a film from the 50's, where they only dared to hint at a kiss, or depict a crime verbally rather than show or the gory details, to todays standards.
Hell, even two decades have made a difference. In my time the only movies that were easily accessible were mainstream hollywood (or equivelent productions). Today you can find anything that your heart desires. It's very easy to find movies, music and games that depict things that the general populace would cringe at.
For someone who already has deep seeded desires to commit a crime it would be easy for them to relate to, or adopt, something that they see in a movie or game. I suspect it's always been this way, it's just that they are now armed, moreso than ever, with knowledge and graphic detail than they would not have been able to access in the past.