What happens when you accidently connect a neutral wire with a hot wire with a screw?
Normally if the proper breaker or fuse was used it would trip the breaker or blow the fuse. Normally the conduit would contain all the damage. Less commonly the fast arc in the pipe will vaporize enough copper that it will clear the fault before the breaker trips.
The wire could be very hard to pull out until the screw is removed, or if the wire is blown clear you can use the wire length to determine where the pipe was damaged.
The damaged piece of conduit should be replaced because the screw penetration will leave a sharp point in the conduit that will tear the insulation on new wire.