Tell me do you think any shooter thinks "Damn... I was gonna shoot people but I forgot that this was a no gun zone... Guess I'll find another spot"

And secondly, by saying that, you acknowledge that there is a possibility of somebody entering your store with the intent to kill, and you believe that chance is high enough that you need a gun to protect yourself and others from them.

Gun control doesn't need to be a total removal of firearms from the people, but in a place like Canada there is an extensive process to getting a gun, that means the only people with access to them are people who will be responsible with them. I know several relatives who have gone through the process to get guns, yes it may be time consuming, but would you rather wait an extra few months to get a gun, or live knowing that there could be another shooting tomorrow.