Only two types of people use guns to murder others. Cowards and mentally unstable people. (Not counting military/enforcement/security/etc applications).
Mentally unstable people, whether their mental illness is permanent or temporary (rage, jealousy, fear, chemically altered, etc..), if they want to kill someone, they are going to try to kill someone no matter what. A gun only facilitates that action. 9 times out of 10, these people will have already cleared the process and obtained guns legally. Unless some kind of futuristic crystal ball DNA scanning device is invented to accurately predict future crimes by these people, you are not going to be able to restrict their access to guns through stricter gun laws and regulation enforcement.
The other people who use guns are just cowards. How many drive by stabbings have you heard of? Take guns away from these individuals and their crime rate will drop drastically because they are just pussies who would never confront someone else in a petty crime effort or bust a knuckle in someone's grill over disrespect or other imagined slights. A gun is a great equalizer for cowards. Unfortunately, all the gun laws and restrictions that could ever be passed won't stop these people from getting them because their first crime is usually in obtaining the gun itself.
Unfortunate situation, but gun control only hurts sane law abiding citizens when they may encounter one of the two examples above. A Catch 22, but there isn't anything that can be done about that.