As I was growing up it was common practise for many people to fill other peoples tags while party hunting although it was never legal in my area.Over the years however this has gotten to be a very controversial topic and it occurs much less frequently than it used to.From an entirely legal standpoint,it would be wrong for you to shoot the deer.Looking at things another way,both of you purchased licenses and tags;both of you stalked the animal and it makes no real difference who killed the deer.Then add in the fact that in my area we have a problem with natives and metis slaughtering game on any land to which they can gain access to legally or otherwise.All that I can say is that I am glad that I was not in your situation and didn't have to make the decision.I can say one thing for sure though,that being that if the person with the tag refused to pull the trigger,I would have another hunting partner or be hunting by myself in the future.I would not allow the same person to put me in that situation again.