Well, the only way for someone to run into you and fall over would be if you made a trigger when you walk into it a waypoint activates and when the enemy walks into another trigger where the enemy dies. I'm not entirely sure it would work like you wanted it to, but that works in its own way
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If you want to know how to script with FPSC, I recommend looking at each of the scripts using Notepad and playing with them. Or you can download FPI Maker from fps-files.net or one of the other fan made sites and that makes making scripts quick and easy.