RPM gauge went whacky when ignition is cut.

[GrandAmMe]

Umm..just noticed when i turned off the car the RPM gauge went to redline for like a millisecond and back. It was almost like it was doing the needle swipe but only on the RPM Gauge and also 10X faster. It never did it again after that. What the hell caused this?:iconfused

[tenspeed]

I shot of voltage caused it. All electrical gauges are basically voltage gauges.