It is certainly possible that you can back feed a transforner on the grid and
kill a lineman, not following his procedures. I doubt it is likely tho. When
your tiny little generator hits that immovable object (your neighbor's loads)
it will trip.
The reality is, if you do kill someone, it is more likely to be your neighbor
who is as electrically dumb as you are and is trying to jury rig something
himself when your generator comes online.
If your lineman does find power coming into the grid from your house, expect to
be on generator long after your neighbors have their power back. Your service
drop will be laying in the yard and your request for service will probably be
"lost in the system" for a while.