It's horrible. I'd also like to know how it happened. Update, found article below..
"Charlie had a bad back, so he went back to his room to rest. And when he came back out, one guy saw a tree move and fired," said a close friend of the victim’s who asked to remain anonymous. Read more: http://www.nydailynews.com/new-york/queens/li-firefighter-shot-friend-mistakes-deer-article-1.1520996#ixzz2l6JkXfqE
That's just not acceptable, friend or not he should be held responsible for negligence.