Steps for working with electricity in the home
Step 1: Turn off the power on that circuit
Step 2: Check that the power to that circuit is actually off (plug something into it, try to switch the light on etc)
Step 3: Treat the bloody wires as if they're live anyway as you're working
Yes, have been burnt (literally) at Step 3. Some (other) Rank Amateur had done the wiring in the attic and got it wrong.
Well, TBF I assume it was a Rank Amateur. For all I know, it may have been a Highly Qualified Professional.