Anyone know how to script an NPC that will insta kill if you look away?

I'm working on an SCP game I really wanna know how to simply script like what the title says. But when I just transfer the 173 free model scripts onto the model it doesnt work. And I try to recreate the whole script but the BodyGyro is outdated. And I wanna know how to simply script it. If you have any answers please do so. Thank you.