Yes, I think we can be ABSOLUTELY CERTAIN that not all of those 10.27 murders per 100,000 population would have taken place had firearms not been readily available.The murders were "caused by a firearm"? You mean had the firearm not existed the murders would not have taken place? Are you sure?
I think you need to do a better job of defending these stats from a US persepctive where the right to bear arms is enshrined in the constitution:
USA 10.27 (unintentional death rate 0.23)
UK 0.46 (0.01)
Germany 1.57 (0.04)
Can you do that? I very much doubt it.