Steven Van Keuren broke into [Teri] Lee's Washington County home and killed her and a friend. Police shot and wounded him.A judge's court order cannot keep you safe - unless of course that order is "held without bail." Just by way of example, the "no contact order" didn't stop him from sending emails - he was not arrested. It didn't stop him from attending a volleyball game in which one of the Lee's daughters was competing. It basically didn't do anything because it was never enforced.
A security system cannot keep you safe. It can keep the average burglar at bay, and call the fire department in the event of a fire, but a security system will not stop someone set on committing violence.
The only thing that can be counted on stop a crazy goblin is a firearm, and even that comes with no guarantee. People who have violent stalkers after them need to prepare to defend themselves everywhere they go, and yes that does include work. If you are disarmed, then you are an easy victim.