I don't think anyone will ever know the truth. The coroner, police, FBI, etc. can write whatever they want on the reports. The problem is you either have an armed society and consequently have a higher murder rate with firearms but a lower overall violent crime rate or you have an unarmed society like the UK where the murder rate is lower with firearms and the violent crime rate is almost 3x what is here. Stats that I have see are that only 300 murders were committed with rifles according to FBI stats. I have heard not seen that only a fraction of those were committed with "assault rifles".