1) What strategies could he practice that he wouldn't already know how to do as a pilot? Is there anything specific that people can think of?
2) While you could argue that some people are inspired by violent video games, I'd hardly say anyone uses them for practice. Such games do not seem very realistic in terms of firing a gun, and usually take place in war zones or in street battles dissimilar to a school environment.
Yup - I've always had an interest in researching drugs and murders, but I've never even gotten an intense argument with someone, and I didn't drink alcohol until age 21. Never done illegal drugs or taken more meds than prescribed. I'm clean as a whistle in my life, but my online history could be used quite badly. One of the young men from Mass. held on terrorism charges at Guantanamo was convicted because he translated some documents into English for jihadist-affiliated people. A huge focus at trial was the fact that he had images of Bin Laden and pro-jihadist images on his computer - not like saved, but in his internet cache. Now try and imagine everything you have in your internet cache, but the public is stupid about that stuff. You have no idea what's in there. I know mine has the JonBenet Ramsey autopsy photos and plenty of other disturbing crime-related images. That doesn't mean I saved them to look at because I enjoy them - and there are people who do save them to keep track of them, but not for any creepy purpose. But it doesn't matter.