It's a cautionary tale -- or should be -- of two cities. In one (Wakefield, Massachusetts), it was the worst of times because only the Bad Guy mass murderer had the guns.

But, in the other city (New York), it was the best of times since a Good Guy also had a gun, knew how to use it, and because of this the Bad Guys are dead.

Describing what happened when seven employees of an Internet consulting company were murdered in cold blood, Middlesex County (MA) District Attorney Martha Coakley said:

"There is an enormous amount of bullets and casings in the building. There was an enormous amount of fire power that occurred in that building today."

The Washington Post said that what happened was a "slaughter." And a surviving co-worker of the employees who were massacred lamented the fact that she was unable to do something "for the people who were there and couldn't get out of the way."

Meanwhile, in the other city, the Big Apple, things turned out quite differently.

Off duty but armed, on Christmas Eve, Detective Michael Zeller went to the Two Flag Deli Grocery in Brooklyn. Zeller was accompanied by his wife Marie, their 3-year-old daughter, and a two-month-old son. They were going to pick up Mrs. Zeller's mother who owns the Deli.

Just about closing time, Jonathan Lynch walked in and asked for a sandwich. Marie Zeller, who was closing up while her Mom left to get her bags from her nearby apartment, said, sure, she'd make him a sandwich.

But, as the New York Daily News reports it, the Zellers became suspicious when Lynch said he wanted to go outside and ask a friend if he also wanted a sandwich. The Zellers watched Lynch chat with his friend, who stood near the open trunk of a parked car.

Michael Zeller studied the two men but dismissed any distrust, telling his wife things looked OK. But, to be sure, he walked outside to take another look. Seconds later, when he headed back into the store, he was staring down the barrel of a .22 caliber revolver pointed at his head. As the first robber ordered the husband to lie on the floor, the second robber held a knife to Marie Zeller's throat, forcing her to empty a cash register.

Suddenly, the Zeller's 3-year-old daughter Devin, who was at her Mom's side, ran from behind the counter and screamed: "Leave my Daddy alone." Daddy yelled to Devin: "Go back." Startled, the robber gunman briefly took his eyes off of Michael Zeller -- a big mistake.

Reaching into his waistband, Zeller pulled out his 9mm Glock pistol and squeezed off five shots. The first two bullets struck the 6-foot, 240-pound James Culbertson in the chest, mortally wounding him. Another shot ripped into the lungs of the 6-foot, 170-pound knife-wielder Lynch, who died at the scene.

Both of the two dead robbers had long criminal records. Police said Lynch's record dated back to 1986, with arrests for assault, grand larceny and armed robbery. Culbertson had been arrested seven times, but six arrests were sealed, apparently because he was a juvenile at the time. In 1999, he was arrested in Queens for robbery and possession of stolen property, but was allowed to plead guilty to a reduced charge of disorderly conduct and sentenced to "community service."

I say that all of this is a cautionary tale -- or ought to be -- of two cities. So, what, exactly, do I mean? Well, in his novel, "A Tale Of Two Cities," Charles Dickens notes, at the beginning, that he writes of a time when, among other things, "it was the age of wisdom, it was the age of foolishness." And so it is in our time regarding guns.

Over and over, ad nauseam, we are told, foolishly, by the Anti-Gun Nuts that guns are the focus of all evil in the world, that they must be banned, that concealed weapons always do more harm than good, blah, blah, blah.

But, this is a lie.

If just one employee at that Wakefield, Massachusetts, Internet consulting firm had possessed a gun, on the job, and knew how to use it, there's at least an even chance there would have been no slaughter. But, a slaughter is what always occurs when only the murderer has guns and his victims do not.

We must be wise and allow our citizens to keep and bear arms because the lives of innocent people, literally, depend on this right.