To be practical, if you are not accustomed to handling deer, (who is?) then if you know who the landowner is, then a call to him or his gamekeeper would be in order. Otherwise, a fence is yet another risk to life and limb with which deer are faced every day. Don't beat yourself up over it, and above all don't be seduced by the over sentimental pap pedalled by the likes of the BBC. Wildlife is exactly what it is.....wild, involving all the risks and hurdles which that entails. At the absolute worst, the deer dies and the meat is wasted, but there are foxes, crows, rooks and badgers which need feeding as well.