This is the bit that cracked me up:
He added: "I didn't realise anything was wrong until I looked down and saw his arm was missing. I ran inside to call the ambulance and he sat outside on a stool.
So there are two options:
1 - the neighbour has a stool at his front door just in case somebody with a severed limb needs to sit down for a moment
2 - the neighbour asked him to wait outside while he fetched a stool
Either way I think they are both heroes. Talk about understated reactions all round...."I didn't realise anything was wrong until he asked me for a stool to sit on..."