Hi vidhi,
as posted by one of our HR mates, did this occur during the course of duty or off duty? take this into consideration.
also check his family and financial background and discuss with his family. if you have someone in his family who can be accommodated in the job, till alternative arrangements are made, then go with it.
However, as a matter of precaution you can, if you are hiring someone from his family, have an agreement that he/she will be in employment only till such time that this person has not recovered. Once this person returns to full working capacity then a call will be taken on that.
also look at the accident from a business point of view. (how valuable was his role in the organisation. was it an accident or sabotaged by any of his rivals or your competitors. don't want to sound like a detective, but no harm in looking at this angle !). also try to work with him/his family to get his memory restored at the earliest. I guess the sooner the better.
I suppose the rest of the employees should, from this incident, know that the company is caring for them and their family (till alternate arrangements are made)
there are no hard and fast rules. you can take this case as an example, frame new rules and share it with us, so that others can take this up further. it's Continual improvement program and work-in-progress