Sorry to hear about your neighbor, hope he recovers.
It's not too hard to overlook this sort of thing, especially if you are tired. When I was younger and worked for a contractor, I plowed snow in the winter time. I had been plowing in a big storm for over 30 hours straight, going from job to job, apartments and office buildings. I was exhausted.
I was at an apartment complex parking lot, and got out of the truck for something, don't remember what now. I put on the parking brake, but accidentally left it in drive. With my back to the vehicle, it started rolling, and the plow blade clipped the back of 7 different vehicles, including a Mercedes, two BMWs and a Jaguar. Not a good day....it happens though. Thankfully, nobody was hurt.
I managed to keep my job, but I heard gaff about that incident for years afterward...and the insurance company was none too happy...