I read two stories today. The first story was about a 24-year-old man who shot and killed a 21-year-old man who attempted to carjack him as he arrived for work on Milwaukee’s notorious northwest side — at 5:50 a.m.

The second story was about a 22-year-old woman who was attacked and stabbed to death inside a public library in Winchester, Mass. She had no chance to defend herself. A 77-year-old man who tried to help her was also stabbed.

The library is a gun-free zone. In fact, it is a violence-free zone. Not only are all weapons banned from library premises, any violence or using any object as a weapon is prohibited. The murderer clearly did not read the library policy. Clearly, the signs offered no deterrence.

I found these stories on the same day as the internet trolls were calling me paranoid and delusional when I claimed that firearms save lives.

What you and I need to remember is that criminals can, and do, strike anywhere. If you think you are safe because you are living in a quiet suburban neighborhood or because you arrive at work before 6 a.m. or because you have found safety and solace among the books of your local library, think again. Criminal predators are mobile. They will go looking for the easiest targets. Do not be one of those easy targets.

The young man in Milwaukee pulled out his own gun and shot the carjacker dead. But consider this: How many of you are expecting to be robbed at approximately 6 a.m.? My guess is you believe nearly all the criminals to be sleeping from bar close until at least noon, right? It’s not like they have jobs to get to. Think again. Criminal activity is their job. And the best time to jack a car is when the person with the keys is getting into or out of that car. That means carjackers will be looking for you as you arrive at work, as you leave work, when you stop for gas and when you pull into your garage after a long day at work. And if the carjacker followed you home from work, you can bet that carjacking will turn into a home invasion as well.

Be prepared. Train to defend yourself in and around your vehicle with your concealed firearm. Think about how you will draw, where you will move and what you will do with your other hand. Remember to keep your strong hand empty and ready for action. Work on shoving your attacker away from you as you try to access your weapon. Be prepared.

As for the young woman in the library, the situation could not have been much worse. By demanding she arrive at the library unarmed, the library board promised to protect her. She was left defenseless as her killer simply ignored the signs and the policy that said “no weapons” in the library.

Avoid gun-free zones. When you follow those rules, you make yourself vulnerable. Be prepared. The attack can come anywhere and at any time.

Criminals follow no rules.