Arming People Doesn't Stop Mass Murders

I was a cop for thirty years. Laws do not stop people from committing crimes. Connecticut has some of the strictest gun laws in the nation. The murderer was 20 years old, between the federal and state laws it was illegal for him to possessed any of the weapons he used to murder these people.
The laws did nothing to stop him.

First of all we do not at this time know what type of weapon was used in the shooting.
I have never understood the idea of limiting what a person can own. There is no difference, to speak of between the amount of rounds that a person can shoot with a 15 round magazine, versus a 10 round magazine. I carried a 7 round .45 for years and was quite comfortable when most of my agency was carrying high capacity .40′s.
The simple fact is that this is all media/politician generated feel good discussion. There are literally millions of high capacity magazines in existence today. Passing a law limiting then will solve nothing.
The question is not why does a law abiding citizen need a semi-automatic version of a military rifle, but why should he be denied access to one. Statically these guns do not exist in the crime stats, criminals do not use them to commit crimes. So banning them will solve nothing, and by the way they were never banned in the last so called ban, you just could not buy one with a flash suppressor and a bayonet lug. Did not effect much, just feel good legislation.
As to your question about the shooter, the problem here, and this is a personal opinion, is the “gun free zone” which all schools are. Nearly every mass shooting in the last 25 years has occurred in a “gun free zone”. It does not take a lot of marksman ship to walk up to people cowering in a corner, because they do not have the ability to defend themselves, and shoot them.
If you want to see this type of thing ended, arm the teachers. Israel did this after several terrorist incidents in schools in the 70′s and they have not had any since.
And M4′s and MP5′s are full auto weapons and not available to the general public. If you have never fired a full auto weapon they are fun to shoot, expensive, but fun, that is what people do with them.

As far as mass shooting with a hunting rifle, try the Texas Bell Tower shooting, 1 August 1966.

The rifle is not a variant of the M16, it is a variant of the simi-automatic AR-15. The difference is in the internal workings of the weapons. The basic design of the simi-automatic has been around since the early 1900’s.
The type of bullets used, I cannot find anything about this and doubt that they were anything special as he stole the gun from his mother and most people use ball(full metal jacketed) for practice. As to your question of if it would have made a difference, no as the victims were all shot multiple times (it appears his intent was to kill as many as possible). And as I said earlier it does not take a large amount of skill to walk up to someone and shoot them.
As to the so called “Cop Killer” and “exploding” bullets (the bullet is the projectile, the entire assembly is called a cartridge or a round) they do not exist. These descriptive (emotional) terms were invented by the politicians/media. I spent years listening to the untruths being told by the anti-firearms crowd about the horrors of certain types of expanding bullets and that they should not be used by law enforcement.
As for the magazines (clips do not have springs in them), there are literally millions of them on the market, most owned by law abiding citizens who will never break any law. These do not in and of themselves cause any problems, they are just another “feel good” item for the politicians and anti-gun folks to rant about. And it takes very little time to reload a magazine fed weapon. An unintended consequence of the Clinton gun ban, with it’s 10 round magazine limit, was that many newly designed compact pistols were made. It does not make sense to make a large gun to hold only ten rounds.
As for your buy back programs, most of that is also feel good politics and does not have any effect on crime. Crooks do not turn in their guns, they just sell them to someone else. Most of the items in the buy back programs are dysfunctional.
The whole thing here is that we are not addressing the two main issues.
1) You cannot respond to an incident like this if you do not have people on the scene. If you have to wait for the police to arrive, it will always be too late. One thing I learned as a cop was that if I needed a weapon, be it pepper spray, Taser or a pistol, I had to have it on my person. I did not have time to go and get it and then respond to the emergency. To prevent this from happening again there must be armed persons in the schools.
2) We must address the mental health laws in this country. The way we take care of people who have mental health issues is a disgrace. The murderer needed help and was not given it. Hind sight is always 20/20 so it is easy to see that almost all of these people who have committed mass murders had mental problems that could have been addressed with a better system.

When last I looked they had not released any information on which weapons were used.

When they are being shot at. If someone is shooting at you, you want to have as many rounds as possible.

Guns with high capacity magazines are the weapon of choice for people that want to protect themselves. Most murders are committed with hand guns.

Hmm…quick reference shows gun crime decreasing btwn 2010-2011 in the UK.

Per capita rates are about 9 per 100000 in the US and 0.25 (that is 1/4) per 100000 in the UK during 2011.

It really is about numbers, not anecdotes

Yes, you are correct, violent crime in England has gone through the roof after the gun ban.