MissHesterMoffit makes a good point, but at this point, just don't tell them anything further unless you have no actual choice.. And that isn't likely to happen since the incident is passed..
My philosophy is the more emphatically ppl trash narcs on the internet, the more likely they are to narc themselves.. For a number of reasons too.. Not only does that scream overcompensation, but its also the typical attitude of your average hot-head.. And who is more likely to find themselves in a position to snitch for their own benefit than an over-compensating hot-head??

Personally I don't worry about snitches.. I approach security from a diligent control perspective.. Nobody can snitch on you if they don't know anything incriminating about you..