I'm trying to decommission an electrical cable that's solidly attached inside the ceiling. it will not budge, I can't pull it out.

I found the junction box, and am sure I have the correct wires disconnected and pushed well away from the box. when I touch each of the other end of the wires with a non-contact voltage tester, they are definitely dead. however, when I jam the tester into the jacket so it's touching the black and white wire at the same time, I get a red light. how on earth?

my only guess: this cable is travelling through the wall next to a live one that goes off into another room (each in their own separate jackets of course). is it possible that the unhooked wire is picking up the tiniest bit of current just from being in proximity to a live wire?

don't fear for my safety. I have a contractor coming in today, he has the proper testing equipment to make sure the wire is really unhooked. I'm just curious how this wire is live.