Some confusing comments on here. America has 40 to 45 murders a day, not 'thousands' (I assume that comment wasn't literal). The worst parts of America have the tightest gun laws and vice-versa.
In another thread I listed numerous cities in South Africa and South America which have enormous levels of homicides - in parts of the world which have tight gun laws. New York has long had tight-arse gun laws as well.
Gun killers in almost every case do not purchase their guns legally as you get registered and stuff. Is that a surprise?