And you obviously don't. There is no recovery, don't feel bad, don't apologize, and don't flame. Be a man, admit you didn't know, learn something, and move on.
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Enough of that tom foolery.
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A-Unit, the media will spin this however it wants. It will likely inject a lot of anti-gun agenda. So the ballistics don't match... yippee - he went home inbetween "sets". He might have thrown away one gun in exchange for another of the same calibre. I have two .22's myself. And, If I'm grouping 10 shots within a quarter-sized area at 25 yards and have only been to the range with my pistol twice... *shrug* his accuracy is very realistic. Have you ever used a red dot scope? It's ridiculous: put the dot where you want the bullet, pull the trigger, done. Easier than a video game - seriously. "Point and shoot simplicity", if you will. Now, pace out 25 yards... I doubt he had any long shots inside a building.
Someone posted a link to a facebook profile or something; the guy's favorite things are guns. He was obviously a fanatic, so his styles probably did appear "professional". There is no telling how much practice he did in preparation or for hobby, so you can't be hasty to jump to an assumption such as he had help.
You can also suspect that he had terrorist funding and training. You can definitely call this a terrorist act, but the real terrorists here are the media.