Have you ever parked your car in a lot that seemed safe in the light of day, but when returning to your vehicle at night it was less than ideal? Many drivers recommend keeping your car key fob in your hand, with your finger covering the “panic” button to call for help. And while the strategy is far from foolproof, it saved at least one woman’s wife.

According to the Albuquerque Journal, 23-year-old Tanya Cass was walking through an Albuquerque parking lot an assailant descended on her. The attacker was armed with a knife and stabbed Tanya. But she was armed with her key fob, so she activated her “panic” button and her assailant fled.

One trendy “life hack” is to leave your car key fob on your bedside table so if you hear someone break into your house, you can activate the alarm to scare them and hopefully signal for help. Barbara Mikkelson of the Snopes fact-checking website had a mixed reaction to this tactic. She points out that many bystanders ignore car alarms.

Mikkelson went so far as to quote a bystander who heard a family’s car alarm go off when burglars broke into a Montreal home: “We all heard the alarm go off but you get desensitized to alarms. I thought it was a car alarm. I said to my daughter I’m going to close the window because that car alarm is bothering me.”

For this reason, Mikkelson recommends your first move is to call 911. It doesn’t matter if someone is coming your way in a parking lot or breaking into your home. Get the authorities on the phone.

What about your car alarm “panic” button? It’s never a bad idea to hit it after you’ve alerted authorities. The sound may help them find you. and while they are on their way it might attract other help. Just don’t count on it.