With the greatest of respect, those are unintelligent questions. One does not need to be a police officer, or a scientist, to know that (a) crazy and/or stupid people exist and (b) if you make it easier for crazy and/or stupid people to get guns, they will use them on innocent people.
There are other factors at work, of course. But those are the big ones. If you don’t get that, you need more help that a newspaper opinion column can provide.
Now, when I was a cop reporter, in Calgary and Ottawa, I noticed that the higher-ups would lay on more officers whenever it was hot, or a full moon, or when school was out. That’s because violent crime tended to go up, noticeably, on those occasions. The reasons, to me, were straightforward: when it got hot, people drank more. When people drank more, they did stupid things, sometimes involving guns.