Oh come on, guns don't murder people; people murder people. However, the easy acquisition of guns in the US is the major cause of so much gun crime, and especially death.
James Homes, the alleged gunman, is a highly intelligent young man. A young man with excellent qualifications, a BSc in Neuroscience. According to colleagues he is a personable man, if "...a bit socially awkward...not to a dgree that would warrant suspicion of mass murder or any atrocity of this nature."
Sadly, the recent killing of 12 people and injuring of a further 60 by a lone gunman, apparently, using automatic weapons legally bought and held is a recurring theme in the land of the free. Time after time presidents have appeared on TV screens after such incidents - there are an average 20 mass shootings every year in the States.
However, in recent times this figure seems to have exploded. Apparently, there have been some 60 mass shootings in the USA since the 2011 massacre in Arizona where 19 people, including the gunman, died in a supermarket car park.
The Second Amendment of the United States Constitution may well state that "A well regulated militia, being necessary to the security of a free State, the right of the People to keep and bear arms shall not be infringed." However, laws are not written in stone; nor are laws passed in order to remain unchallenged in perpetuity.
With the passage of time comes change; and the 'well regulated militia' of some 220+ years needed to be ready to suppress and defend the State against tyrant European Princes is no longer needed.
It is not needed, nor has it been, for a long time. The USA has a national structure of armed forces as well as diverse law enforcement agencies. The idea that a European power, or any other power coming to that, will begin imposing unfair taxes and laws upon a modern US is not feasible. The very reason for the existence of the Second Amendmet, and for the right of ordinary citizens to bear arms is an anachronistic freedom; it is a indefensible freedom claimed by those of a conservative leaning, particularly those on the political right.
While amending the Second Amendment in order to put greater regulation on gun ownership would not necessarily stop people killing one and other; nor would it entirely stop people murdering others with guns. What it would probably achieve is to put an end to these senseless mall, cinema and high school massacres that occur with too great a regularity.