How do I use multiple characters with line of sight?

Hey. I have a 2D sidescroller where the enemies don't shoot at the player unless he's near, they can spot him using line of sight. Problem is, when one detects him, they all do! Am I missing something, is there a better way to do this?

Thanks for help.

You've probably set your events/conditions up in a way that picks all enemy instances instead of just the one(s) that has/have the line of sight..

Please share your events, so it's possible to assist..