And you're alive to talk about it...

What do you mean "I touched the wires for a second"? I'd guess that you touched the in-wall black to the white, bare or something that was grounded and the breaker worked as designed. I recommend that you turn the breaker off as your first step next time.

This is a good example of why turning off the switch isn't always enough. ALWAYS turn off the breaker when working on a circuit.

I wonder if your switch is wired up to break the neutral instead of the hot. Otherwise, with just those wires, I don't think anything SHOULD have been live in a properly wired lighting circuit. I'd open up the switch box and look at how that's wired.

Was this on a GFCI? If so and you actually touched the wires with your fingers instead of touching the wires together (like randy suggested) then you can thank your lucky stars that it actually was a GCFI. It may have saved your life.

Thanks for the help Randy and Greg. I was definitely touching all the wires throughout the process and luckily I didn't get zapped.

It's a really good possibility that while I was pulling out the in wall wires I may have touched them together briefly? Because as I was doing that my wife said the TV turned off.

I will ALWAYS turn off the breaker going forward, I thought turning off the three way switch would work but obviously it didn't.

And yes - I think I have GCFI. There's a test button on the breaker that went off...does that mean it's GFCI?

I thought turning off the three way switch would work but obviously it didn't.

Well, there's your problem. A three way switch doesn't have an 'off'. It has an up and a down and depending on the orientation of the second switch, either position could actually turn the light off.

So you probably didn't have the light turned off before you started fiddling with it.

Re: GFCI

Yes the test button means it's GFCI. This device is an extra safety precaution that quickly breaks the circuit if there is even a slight imbalance on the hot/neutral (like if the current is flowing through your body into the ground.) Normal circuit breakers only trip on an overload, which is way more electricity than is required to stop your heart.

Turning off the breaker is the start of the process. Always. But that is not a fool proof solution. You should also always test the circuit with a properly functioning non contact voltage tester or a multimeter set to AC voltage. Testing ensures that you turned the correct breaker off and you are safe to work on the electric.

Cheap voltage testers can read false positives over time. I recommend the Klein tools tester which shows less false positives and allows you to differentiate which wires are live if you have multiple lines running near each other.

"There's a test button on the breaker that went off"

Even if the switches were in the correct position so that the black wire was not hot when you were working on the light, you can still trip a GFCI by touching the white wire (neutral) to the bare copper wire (ground). If it didn't spark when you touched the wires, the trip is not likely to be caused by a short circuit. You probably tripped the GFCI by adding a second ground path to the neutral (grounded conductor). All GFCIs will trip if you touch the neutral to ground as it senses the current in both the hot and neutral.

3-way switches are complicated but in general for regular fixtures, the power line goes to the fixture, then the black (hot) wire goes down to the switch and back. Which means turning off the switch on a regular fixture does nothing to shut off the power still coming into the fixture!

but in general for regular fixtures, the power line goes to the fixture,
then the black (hot) wire goes down to the switch and back.

That's called a switch loop and while it is common, I don't know if it's more common than having power go to the switch and then on to the fixture. It all depends on the specific layout of the house in question as to which way is better (ie. uses less wire)

And while a switch loop will have power still present in the fixture's box, it isn't actually one of the wires that is attached to the fixture itself. Those wires are still just the neutral and the switched hot coming back from the switch. The constant hot is wirenuted (is that a term?) to the wire going to the switch and tucked into the back of the box. No need to touch that if you are replacing the fixture.

But as we've all stated, you should still turn off the breaker.